APPROXIMATE GATE AND SUPERCONTROLLED UNITARY GATE DECOMPOSITIONS FOR TWOQUBIT OPERATIONS

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First Claim
1. A computerimplemented method, comprising:
 expanding, by a system operatively coupled to a processor, using N number of applications of a specific super controlled basis gate of the one or more super controlled basis gates, wherein N is an integer, a target twoqubit operation, wherein the expanding results in instances of the target twoqubit operation corresponding to the N number of applications, and wherein the target twoqubit operation is part of a source quantum circuit associated with a quantum computer;
analyzing, by the system, the instances and the specific super controlled basis gate; and
rewriting, by the system, the source quantum circuit into a deployed quantum circuit based on the analyzing.
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Abstract
Techniques are provided for improving quantum circuits. The technology includes approximately expanding, by a system operatively coupled to a processor, using zero to a number of applications of a super controlled basis gate, a target twoqubit operation, with the approximately expanding resulting in instances of the target twoqubit operation corresponding to the zero to the number of applications, and the target twoqubit operation is part of a source quantum circuit associated with a quantum computer. The system analyzes the instances and the super controlled basis gate, and automatically rewrites the source quantum circuit into a deployed quantum circuit based on the analyzing.
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25 Claims
 1. A computerimplemented method, comprising:
expanding, by a system operatively coupled to a processor, using N number of applications of a specific super controlled basis gate of the one or more super controlled basis gates, wherein N is an integer, a target twoqubit operation, wherein the expanding results in instances of the target twoqubit operation corresponding to the N number of applications, and wherein the target twoqubit operation is part of a source quantum circuit associated with a quantum computer; analyzing, by the system, the instances and the specific super controlled basis gate; and rewriting, by the system, the source quantum circuit into a deployed quantum circuit based on the analyzing.  View Dependent Claims (2, 3, 4, 5, 6)
 7. A computerimplemented method, comprising:
expanding, by a system operatively coupled to a processor, using N number of applications of a specific super controlled basis gate of a specific super controlled basis gates, wherein N is an integer, a target twoqubit operation, wherein the expanding results in instances of the target twoqubit operation corresponding to the N number of applications, wherein the target twoqubit operation is part of a source quantum circuit associated with a quantum computer, and wherein the instances comprise expansions of both the target twoqubit operation and the target twoqubit operation concatenated with an exchange of the two qubits; determining, by the system, an average fidelity of at least one of the expanded instances; and rewriting, by the system, the source quantum circuit into a deployed quantum circuit based on the average fidelity of at least one of the expanded instances.  View Dependent Claims (8, 9, 10, 11, 12, 13)
 14. A system, comprising:
a processor that executes computer executable components stored in memory, wherein the computer executable components comprise; a circuit expanding component that expands, using N number of applications of a specific super controlled basis gate, wherein N is an integer, an identified block of consecutive operations on pairs of qubits, wherein the expanding results in instances of the identified block corresponding to the N number of applications, and wherein the identified block is part of a source quantum circuit associated with a quantum computer; an analyzer component that analyzes the instances; and a circuit rewriting component that rewrites the source quantum circuit into a quantum processing unit (QPU) hardware circuit based on the analyzing analysis of the instances.  View Dependent Claims (15, 16)
 17. A computerimplemented method, comprising:
expanding, by a system operatively coupled to a processor, using N number of applications of a basis gate, wherein N is an integer, a target twoqubit operation, wherein the expanding results in instances of the target twoqubit operation corresponding to the N number of applications, wherein the basis gate is selected based on a similarity to a super controlled basis gate, and wherein the target twoqubit operation is part of a source quantum circuit associated with a quantum computer; analyzing, by the system, the instances; and rewriting, by the system, the source quantum circuit into a deployed quantum circuit based on the analyzing the instances.  View Dependent Claims (18, 19, 20, 21, 22, 23)
 24. A computer program product facilitating rewriting a source quantum circuit into a deployed quantum circuit associated with a quantum computer, the computer program product comprising a nontransitory computer readable storage medium having program instructions embodied therewith, the program instructions executable by a processor to cause the processor to:
expand, using N number of applications of a specific super controlled basis gate, wherein N is an integer, a target twoqubit operation, wherein the expanding results in instances of the target twoqubit operation corresponding to the N number of applications, and wherein the target twoqubit operation is part of a source quantum circuit associated with a quantum computer; analyze the instances and the specific super controlled basis gate; and rewrite the source quantum circuit into a deployed quantum circuit based on the analyzing.  View Dependent Claims (25)
1 Specification
The subject disclosure relates to quantum circuits, e.g., quantum circuit design. Quantum computing employs quantum physics to encode and process information, rather than binary digital techniques based on transistors. A quantum computing device employs quantum bits (also referred to as qubits) that operate according to the laws of quantum physics and can exhibit phenomena such as superposition and entanglement. The superposition principle of quantum physics allows qubits to be in a state that partially represent both a value of “1” and a value of “0” at the same time. The entanglement principle of quantum physics allows qubits to be correlated with each other such that the combined states of the qubits cannot be factored into individual qubit states. For instance, a state of a first qubit can depend on a state of a second qubit. As such, a quantum circuit can employ qubits to encode and process information in a manner that can be significantly different from binary digital techniques based on transistors. However, the designing of quantum circuits often can be relatively difficult and/or time consuming
With regard to quantum circuit design, a conventional approach can use a universal quantum computing circuit that can be utilized for virtually all types of algorithms The universal quantum computing circuit typically can have qubits that can be connected to all of their neighbor qubits, and typically can run all or virtually all types of algorithms, although with varying and/or limited levels of performance, due at least in part to, for example, resource limits and design constraints, as well as the universal nature of the connectivity of the qubits in the universal quantum computing circuit.
Another conventional approach to improving the operation of quantum circuits involves identifying twoqubit operations (corresponding to one or more twoqubit gates) in a circuit and trying to simplify them. One way to simplify a gate is to either approximate or expand the twoqubit gate by different processes. Universal gates can be used to expand the gates to be simplified, though because of their varying and/or limited levels of performance, their use often does not simplify a circuit.
An example of a universal gate that is known to be able to simplify some twoqubit gates is a super controlled gate. Any operation on twoqubits can be implemented using at most three super controlled gates. Operations on twoqubits can also be termed Special Unitary (4) operations (SU(4)). One type of super controlled gate is the controlled NOT (CNOT) gate and it is known that, as a super controlled gate, any operation on twoqubits can be implemented using zero or at most three CNOT gates.
With these known approaches to improving the operation of quantum circuits however, there are problems. The conventional approaches noted above only use a discrete singlequbit basis set for expanding expressions. Based on this limited basis set, these approaches have a problem accurately handling a variety of different expressions without significant inaccuracy. These approaches also do not perform simplification operations while considering performance problems that can result from the use of certain twoqubit gates, e.g., they fail to consider problems with inaccuracies that can result from the use of certain twoqubit gates and/or certain numbers of the same twoqubit gates. These and other problems of conventional quantum computing circuit design approaches can result in inaccuracies as well as inefficient and/or ineffective circuits and/or inefficient performance of a quantum circuit design.
The following presents a summary to provide a basic understanding of one or more embodiments of the invention. This summary is not intended to identify key or critical elements, or delineate any scope of the particular embodiments or any scope of the claims. Its sole purpose is to present concepts in a simplified form as a prelude to the more detailed description that is presented later.
According to an embodiment, a computerimplemented method can comprise approximately expanding, by a system operatively coupled to a processor, using zero to a number of applications of a super controlled basis gate, a target twoqubit operation and the approximately expanding can result in instances of the target twoqubit operation corresponding to the zero to the number of applications, and the target twoqubit operation is part of a source quantum circuit associated with a quantum computer. The system can analyze the instances and the super controlled basis gate, and automatically rewrite the source quantum circuit into a deployed quantum circuit based on the analyzing. The computerimplemented method can have a number of advantages, including that automatically rewriting the source quantum circuit into the deployed quantum circuit based on embodiments can improve processing performance and accuracy of the deployed circuit, with embodiments providing an efficient mechanism to determine whether to use approximate or exact expansions of the target twoqubit operations.
According to another embodiment, a computerimplemented method can comprise approximately expanding, by a system operatively coupled to a processor, using zero to a number of applications of a super controlled basis gate, a target twoqubit operation, and the approximately expanding results in instances of the target twoqubit operation corresponding to the zero to the number of applications. The target twoqubit operation can be part of a source quantum circuit associated with a quantum computer, and the instances comprise both the target twoqubit operation and the target twoqubit operation concatenated with an exchange of two qubits and the target twoqubit operation. The system determines an average fidelity of at least one of the approximately expanded instances and automatically rewrites the source quantum circuit into a deployed quantum circuit based on the average fidelity of at least one of the instances. In an aspect, automatically rewriting the source quantum circuit into the deployed quantum circuit can improve processing performance of the deployed quantum circuit. The computerimplemented method can have a number of advantages, including that automatically rewriting the source quantum circuit into the deployed quantum circuit based on embodiments can improve processing performance and accuracy of the deployed circuit, as well as consideration of mirror operations associated with the target twoqubit operation.
According to yet another embodiment, a system can comprise a memory that stores computer executable components and a processor that executes computer executable components stored in the memory, with the computer executable components comprising a circuit expanding component that approximately expands, using zero to a number of applications of a super controlled basis gate, an identified block of consecutive operations on pairs of qubits. The approximately expanding results in instances of the identified block corresponding to the zero to the number of applications, and the identified block is part of a source quantum circuit associated with a quantum computer. An analyzer component that analyzes the instances and a circuit rewriting component that rewrites the source quantum circuit into a quantum processing unit (QPU) hardware circuit based on the analyzing the instances. The system can have a number of advantages, including that automatically rewriting the source quantum circuit into the circuit based on embodiments can improve processing performance and accuracy of the deployed circuit, with embodiments providing an efficient mechanism to determine whether to use approximate or exact expansions of the target twoqubit operations.
According to another embodiment, a computerimplemented method can comprise approximately expanding, by a system operatively coupled to a processor, using zero to a number of applications of a basis gate, a target twoqubit operation, with the approximately expanding resulting in instances of the target twoqubit operation corresponding to the zero to the number of applications and the basis gate is selected based on a similarity to a super controlled basis gate. The target twoqubit operation is part of a source quantum circuit associated with a quantum computer. The system analyzes the instances and automatically rewrites the source quantum circuit into a deployed quantum circuit based on the analyzing the instances. The computerimplemented method can have a number of advantages, including that automatically rewriting the source quantum circuit into the deployed quantum circuit based on embodiments can improve processing performance and accuracy of the deployed circuit, including selection of a basis gate based on a similarity to a super controlled basis gate.
According to yet another embodiment, a computer program product facilitating rewriting a source quantum circuit into a deployed quantum circuit associated with a quantum computer can comprise a computer readable storage medium having program instructions embodied therewith. The program instructions are executable by a processor to cause the processor to approximately expand, by a system operatively coupled to a processor, using zero to a number of applications of a super controlled basis gate, a target twoqubit operation, with the approximately expanding resulting in instances of the target twoqubit operation corresponding to the zero to the number of applications, and the target twoqubit operation is part of a source quantum circuit associated with a quantum computer. The instructions further cause the processor to analyze the instances and the super controlled basis gate and automatically rewrite the source quantum circuit into a deployed quantum circuit based on the analyzing. The computer program product can have a number of advantages, including that automatically rewriting the source quantum circuit into the deployed quantum circuit based on embodiments can improve processing performance and accuracy of the deployed circuit, with embodiments providing an efficient mechanism to determine whether to use approximate or exact expansions of the target twoqubit operations.
The following detailed description is merely illustrative and is not intended to limit embodiments and/or application or uses of embodiments. Furthermore, there is no intention to be bound by any expressed or implied information presented in the preceding Background or Summary sections, or in the Detailed Description section.
One or more embodiments are now described with reference to the drawings, wherein like referenced numerals are used to refer to like elements throughout. In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a more thorough understanding of the one or more embodiments. It is evident, however, in various cases, that the one or more embodiments can be practiced without these specific details.
Quantum computing employs quantum physics to encode information, in contrast to binary digital techniques based on transistors. For example, a quantum computer can employ quantum bits (e.g., qubits), which are basic units of quantum information. Qubits operate according to a superposition principle of quantum physics and an entanglement principle of quantum physics. The superposition principle of quantum physics states that each qubit can represent both a value of “1” and a value of “0” at the same time. The entanglement principle of quantum physics states that qubits in a superposition can be correlated with each other. For instance, a state of a first value (e.g., a value of “1” or a value of “0”) can depend on a state of a second value. As such, a quantum computer can employ qubits to encode information and employ qubit operations (or qubit gates) to modify qubits for quantum processing.
To facilitate processes, store results, and provide storage for processor executable components, system 150 accesses memory 165 and storage 170, these respectively being, for example, Random Access Memory (RAM) and a hard drive. Processing component 160 can receive executable instructions from memory 165 and storage 170 and execute functional components, such as 152, 154, and 156 discussed above.
System 150 can process quantum circuit data 130 (also termed ‘source quantum circuit data’) and provide results to quantum computer 120, the results being, for example, modified quantum circuit data executable by quantum processing component 125, e.g., a quantum processing unit (QPU) (also termed ‘deployed quantum circuits’). Other aspects of an operating environment in which one or more embodiments described herein can be facilitated is discussed further below with a discussion of
To provide a solution to the problem of simplifying quantum circuits, circuit expanding component 152 can receive quantum circuit data 130 (also termed ‘target operations’ and ‘target gates’) and can expand one or more target operations according to different criteria (not shown in
In an example, to expand a target operation, one or more embodiments generate instances of the target operation corresponding to multiple instances of an application of the basis gate. The number of instances generated can be selected based on characteristics of the basis gate, i.e., when the basis gate selected is a CNOT gate, four expressions are generated by embodiments, including for example four instances of the following: use of no CNOT gates, use of one CNOT gate, use of two CNOT gates, and use of three CNOT gates.
It should be noted that, for the instances generated by embodiments that duplicate an operation exactly (e.g., by using threesuper controlled basis gates) the simplification by these instances can be termed an expansion, while when instances are an approximation of a target operation, the simplification of these instances can be termed an approximation. Because one or more embodiments simplify exactly and approximately, expansions discussed herein can be termed approximate expansions. For convenience, these approximate expansions can also be termed as expansions herein.
As discussed further herein, one or more embodiments consider a tradeoff between a reduction in fidelity and an increase in performance when implementing the resulting expression, i.e., there can be advantages to designing circuits considering some of the competing considerations discussed above.
In one or more embodiments, instances of the target operation generated by circuit expanding component 152 can be analyzed by analyzer component 154 based on different criteria. One approach used by embodiments employs a determined measure of the fidelity of the instance to the original target operation. It should be noted that, because determinations of fidelity by one or more embodiments are generally directed to a fidelity predicted to be realized when an expression is implemented, expressions of determined fidelity discussed herein can also be termed “predicted” fidelity.
Another approach considers the number and type of basis gates used to generate the expression, e.g., CNOT gates are known to potentially introduce inaccuracies and cause performance problems, so instances having fewer of these gates can be preferred by one or more embodiments. Other approaches of evaluating instances for use are discussed below.
In one or more embodiments, once instances have been analyzed, an instance can be selected based on different criteria for rewriting by circuit rewriting component 156. Rewriting generally involves using a selected instance of the target operation to generate a new operation (also termed an ‘deployed quantum circuit’) for use with quantum computer 120.
The system 150 can employ hardware and/or software to solve problems that are highly technical in nature, including expanding, evaluating, and redesigning quantum circuit data, that are not abstract and that cannot be performed as a set of mental acts by a human. Further, in certain embodiments, some of the processes performed can be performed by one or more specialized computers (e.g., one or more specialized processing units, a specialized computer such as tomography and reconstruction, statistical estimation, and so on) for carrying out defined tasks related to machine learning. The system 150 and/or components of the system 150 can be employed to solve new problems that arise through advancements in technologies mentioned above, computer architecture, and/or the like.
One or more embodiments of the system 150 can provide technical improvements to operations performed by quantum circuit systems, quantum processor systems, quantum computing systems, artificial intelligence systems, and/or other systems. One or more embodiments of the system 150 can also provide technical improvements to operations performed by quantum processor (e.g., a superconducting quantum processor) by improving processing performance of the quantum processor, improving processing efficiency of the quantum processor, improving processing characteristics of the quantum processor, improving timing characteristics of the quantum processor and/or improving power efficiency of the quantum processor. All of the abovediscussed quantum computer processors can be represented by quantum processing component 125.
In this example, in block 225, super controlled twoqubit basis gate 227 is selected as an basis gate for expanding the target operation. This process provides expansion information for use by block 220, approximately expanding the target operation using the selected basis gate. In an embodiment, this basis gate used can be preset or selected from an available group of basis gates based on different criteria. One approach used for these criteria uses characteristics of a quantum computer for which modified target expressions are to be used (e.g., quantum computer 120 receiving a deployed circuit from system 150). Thus, in one or more embodiments, characteristics of a quantum computer are determined and these characteristics are used to select a specific basis gate of a collection of basis gates.
In block 220, instances of target operation 212 are generated (i.e., target operation 212 is approximately expanded) with the selected super controlled twoqubit basis gate 227. In one or more embodiments, instances can be created by varying the number of uses of the selected basis gate in different instances. In this example, for super controlled twoqubit basis gate 227, the number of gates used by instances can vary from zero (0) to three (3). As noted above, and as would be appreciated by one having skill in the relevant art(s), given the description herein, any given operation on twoqubits can be implemented using from zero to at most three super controlled twoqubit basis gates. Creating instances for comparison using 03 super controlled gates is thus an efficient way of generating instances (i.e., any more than 3 could degrade performance and slow the instance creating process). For generating instances by one or more embodiments, different numbers of gates could also be used for different target operations. In this example, using super controlled twoqubit basis gate 227, four instances 222 are generated and passed to block 230.
In block 230, the instances of the target operation are analyzed by embodiments based on different criteria. In this example, fidelity is generated for the instances according to processes discussed in more detail with the description of
In block 240, an instance of the generated instances (e.g., one of 0, 1, 2, 3 uses of super controlled twoqubit gate) is selected based on measurements generated in block 230. In an embodiment, the selected instance is rewritten (i.e., a new version of the original target operation 212 or source quantum circuit) to a deployed quantum circuit 242 (i.e., one that is in a condition for execution by quantum processing component 125). In this example, of the four instances 232 with 0, 1, 2, or 3 uses (also termed ‘applications’) of super controlled twoqubit basis gate 227, one is selected with the highest fidelity, as generated during the process described with block 230. These processes are discussed in more detail with the description of
Moreover, because at least the expanding target operations, analyzing the instances of expanded target operations, selecting instances, and generating (also termed ‘rewriting’) quantum circuits for use on a quantum computer (also termed ‘deployed quantum circuits’), are established from a combination of electrical and mechanical components and circuitry, a human is unable to replicate or perform processing performed by the embodiments described herein, e.g., system 150 and the computer implemented methods shown in
Operation 302 represents approximately expanding, using zero to a number of applications of a super controlled basis gate, a target twoqubit operation, resulting in instances of the target twoqubit operation corresponding to the zero to the number of applications, the target twoqubit operation being part of a source quantum circuit associated with a quantum computer. Operation 304 represents analyzing the instances and the super controlled basis gate. Operation 306 represents automatically rewriting, by the system, the source quantum circuit into a deployed quantum circuit based on the analyzing.
At least one embodiment of operation 302 (e.g., performed by circuit expanding component 152 in system 150 and represented by block 220 of
(K_{1}^{l}⊗K_{1}^{T})·U_{d}(α, β, γ)·(K_{2}^{l}⊗K_{2}^{t})
U_{d}(α, β, γ)=e^{1(α⊗σ}^{x}^{σ}^{x}^{+βσ}^{y}^{⊗σ}^{y}^{+γσ}^{z}^{⊗σ}^{z}^{) } Equations #1
With respect to equations #1, one having skill in the relevant art(s), given the description herein, would appreciate that the operators K are singlequbit operations in SU(2) and U_{d}(α, β, γ) is a threeparameter family of twoqubit operations. One or more embodiments described herein expand the target operation to generate instances of the target operation by processing a representation of the target operation in U_{d}(α, β, γ) form and modifing the α, β, γ coefficients according to particular criteria, e.g., based a number (e.g., 04) of super controlled basis gates applied to generating a revised version (instance) of the target operation to be analyzed (e.g., by operation 304). One having skill in the relevant art(s), given the description herein, would appreciate that the basic approach described above (expanding into instances for analysis, etc.) can be performed using other approaches, without departing from the scope and spirit of the embodiments described herein.
Examples of the operations used to expand a target operation and generate instances are included below. In this example, the basis gate used is a super controlled twoqubit basis gate (in this example a CNOT gate) and has U_{d}(α, β, γ) corresponding to equation #2 below:
U_{d}(π/4, β, 0) Equation #2
Given the above example, the equations (3, 4, 5, 6) below can be used by one or more embodiments to approximately expand a U_{d}(α, β, γ) form of the target operation using 0, 1, 2, and 3 super controlled basis gates respectively.
U_{d}(0, 0, 0) Equation #3
U_{d}(π/4, β, 0) Equation #4
U_{d}(α, β, 0) Equation #5
U_{d}(α, β, γ) Equation #6
Continuing this example, embodiments of operation 304 (e.g., block 230 and analyzer component 154) can be used to analyze the instances generated by equations 36 above. In one or more embodiments, the fidelity of an instance as generated above can be determined by approximating a target gate (generated instance) equivalent to equation #7 below, by a basis gate (also termed ‘implemented gate’) equivalent to equation #8 below.
U_{d}(α_{target}, β_{target}, γ_{target}) Equation #7
U_{d}(α_{imp}, β_{imp}, γ_{imp}) Equation #8
Based on the target gate and implemented gate respectively described by equations #7 an #8 above, one or more embodiments can determine an average fidelity (F_{avg}) of the target gate, using optimal single qubit pre and postrotations, by employing equation #9 below where equation #10 describes the coefficients of equation #9.
Thus, based on the operation of embodiments and the descriptions above the total fidelity (including the fidelity of each instance, e.g., due to use of 0, 1, 2, or 3 basis gates (e.g., super controlled twoqubit basis gate 227) can be described by the set of equations below, labeled as equations #11. These equations can also be described as determining a maximum predicted fidelity of the instances, this maximum predicted fidelity being based on multiplying the average fidelity of the instance by a predicted fidelity of a super controlled basis gate raised to a power of a total number of the super controlled basis gates used by the instance.
Based on the above equations, in at least one embodiment, constructions such as is represented by equation #11B can be determined, where coefficients are set as specified in equations #11C below:
(K_{1,target}^{l}⊗K_{1,target}^{T})·U_{approx}·(K_{2,target}^{l}⊗K_{2,target}^{T}) Equation 190 11B
U_{approx}^{(0)}=U_{d}(0, 0, 0),
U_{approx}^{(1)}=U_{d}(α_{basis}, β_{basis}, γ_{basis}),
U_{approx}^{(2)}=U_{d}(α_{target}, β_{target}, 0),
U_{approx}^{(3)}=U_{d}(α_{target}, β_{target}, γ_{target}) Equations #11C
Continuing this example, embodiments of operation 306 (e.g., block 240 and circuit rewriting component 156) can be used to rewrite the target circuit based on the analyzing operations described in equations 711 and throughout this disclosure. One approach to employing the analyzing results to rewrite the target operation is to compare the generated instances (e.g., generated by equation 36) by some criteria, for example, the determined fidelity of each instance due to each use of the basis gate by the instance (also termed ‘F_{basis}’) (as generated by equations 711). In one or more embodiments where fidelity is determined on a basis of comparing generated instances, the instance with the highest overall fidelity over the set {F_{i}, i=0 . . . 3} can be selected as an instance for rewriting into a deployed quantum circuit.
In an alternative embodiment that involves differences in expansion of target operations by operation 302 above, before expansion by the processes discussed above, operations in U_{d}(α, β, γ) are modified to improve the final result. In this embodiment, it is preferred that any duplicate representations of operations in U_{d}(α, β, γ) y) and the basis gate be removed from consideration such that only unique α, β, γ coefficients are expanded and considered. One approach to removing these duplicates is to employ Weyl chamber representation of the target operation and basis gate in U_{d}(α, β, γ) form. For example, with respect to the representation of the target operation shown in equation #1 above (CNOT), equation #12 below represents restriction by a Weyl chamber representation.
In one or more embodiments, after an expression is modified based on the Weyl chamber representation, the expanding of that expression is not approximate, rather is it exactly expanded.
It should be noted that this Weyl chamber representation of a target operation can be used in place of the target operations discussed herein, and the examples discussed herein where a target operation is referenced can also be considered as implemented by employing a Weyl chamber representation of the target operation.
Additionally, it should also be noted that, as described above, to accurately expand a variety of expressions, one or more embodiments described herein can employ a continuous set of singlequbit gates in SU(2) for expanding expressions (if a QPU is able to execute arbitrary singlequbit SU(2) operations exactly), in addition to approximately expanding SU(2) expressions from discrete singlequbit basis gates if required. Because existing approaches only use discrete singlequbit basis gates (i.e., not also employing a continuous set of singlequbit gates in SU(2) as in one or more embodiments), one or more embodiments solve the conventional problems with flexibly handling different expressions with negligible inaccuracy.
For any operation expressed as in equation #1 above, then a swap (also termed U.SWAP or “mirror” gate) performed on the expression can be described by equation #13 below, where the sign function (SGN(x)) gives −1 for x<0 and +1 for x>0:
U_{d}(π/4−γ, π4−β,sgn(γ)(α−π/4)) Equation #13
The above swap expression can also be described as the target operation being concatenated with an exchange of two qubits and the target twoqubit operation.
In this embodiment, the generated instances include both the expanded target twoqubit operation and the expanded target twoqubit operation concatenated with an exchange of two qubits and the target twoqubit operation. In this embodiment, operation 406 can select instances for rewriting further based on the use (or not) of the swap operations by the analyzed instance. Adding this consideration of mirror operations can further facilitate the solving of problems associated with simplification of quantum circuits, e.g., accuracy and performance can be improved.
In one or more embodiments that generate swap instances as described above, the instance selected for rewriting (e.g., by operation 406) can be further based on minimizing a number of swap operations required to implement a containing quantum circuit of the source quantum circuit.
In this alternative embodiment, the basis gate is not a super controlled gate. In one or more embodiments, the basis gate selected for expansion by operation 502 can be selected based on a similarity to a super controlled basis gate. With this approach to selection deviations due to differences between the basis gate and the super controlled basis gate can be reduced by local optimization of singlequbit gates by fine tuning results of the approximately expanded target twoqubit operation. An example of the fine tuning that can be used by this alternative embodiment employs a gradientdescent algorithm to reduce the deviations due to differences between the basis gate and the super controlled basis gate by acting on the singlequbit gates.
For simplicity of explanation, the computerimplemented methodologies are depicted and described as a series of acts. It is to be understood and appreciated that the subject innovation is not limited by the acts illustrated and/or by the order of acts, for example acts can occur in various orders and/or concurrently, and with other acts not presented and described herein. Furthermore, not all illustrated acts can be required to implement the computerimplemented methodologies in accordance with the disclosed subject matter. In addition, those skilled in the art will understand and appreciate that the computerimplemented methodologies could alternatively be represented as a series of interrelated states via a state diagram or events. Additionally, it should be further appreciated that the computerimplemented methodologies disclosed hereinafter and throughout this specification are capable of being stored on an article of manufacture to facilitate transporting and transferring such computerimplemented methodologies to computers. The term article of manufacture, as used herein, is intended to encompass a computer program accessible from any computerreadable device or storage media.
System 150 can employ any suitable machinelearning based techniques, statisticalbased techniques and/or probabilisticbased techniques. For example, the circuit rewriting component 110 can employ expert systems, fuzzy logic, SVMs, Hidden Markov Models (HMMs), greedy search algorithms, rulebased systems, Bayesian models (e.g., Bayesian networks), neural networks, other nonlinear training techniques, data fusion, utilitybased analytical systems, systems employing Bayesian models, etc. In another aspect, system 150 can perform a set of machine learning computations associated with generation of the deployed quantum circuits, such as the use of: clustering machine learning computations, a set of logistic regression machine learning computations, a set of decision tree machine learning computations, a set of random forest machine learning computations, a set of regression tree machine learning computations, a set of least square machine learning computations, a set of instancebased machine learning computations, a set of regression machine learning computations, a set of support vector regression machine learning computations, a set of kmeans machine learning computations, a set of spectral clustering machine learning computations, a set of rule learning machine learning computations, a set of Bayesian machine learning computations, a set of deep Boltzmann machine computations, a set of deep belief network computations, and/or a set of different machine learning computations.
To further provide a description of at least one embodiment, additional detailed descriptions of approaches described above are included below.
An arbitrary twoqubit unitary can be decomposed in the form:
U=(K_{1}^{l}⊗K_{1}^{γ})U_{d}(α, β, γ)(K_{2}^{l}⊗K_{2}^{γ}) (1)
where K^{l,r }are singlequbit unitaries.
U_{d}(α, β, γ)=exp[i(ασ_{x}⊗σ_{x}+βσ_{y}⊗σ_{y}+γσ_{z}⊗σ_{z})], (2)
The Weyl chamber is also used by some embodiments in the form π/4≥α≥β>γ. For the formulas included below, expression “A˜B” can be used to denote equivalence between A and B under local operations.
At least one embodiment determines the trace between two U_{i}=Ud(α_{i},β_{i},γ_{i}) as:
Tr(U_{1}^{t}U_{2}=4 cos(Δ_{α})cos(Δ_{β})cos(Δ_{γ})−4i sin(Δ_{α})sin(Δ_{β})sin(Δ_{γ}), (3)
where
Δ_{α}=α_{1}−α_{2}, (4a)
Δ_{β}=β_{1}−β_{2}, (4b)
Δ_{γ}=γ_{1}−γ_{2}. (4c)
From the trace, the average gate fidelity can be determined by at least one embodiment as:
Using this approach also provides, in some embodiments, the maximal fidelity between arbitrary SU(4) unitaries after optimizing over local pre and postrotations.
At least one embodiment can determine the decompositions of a target unitary U_{t}∈SU(4) with the minimal number of uses of a fixed ‘basis’ gate U_{b}. In an example, with 0 uses of the basis nonentangling target unitaries Ut˜Ud(0, 0, 0) can be constructed, and with 1 use of the basis only target unitaries which are equivalent to the basis Ut˜U(α_{b},β_{b},γ_{b}) can be constructed. For U_{b}˜CNOT U_{d}(π/4, 0, 0), for example, three uses of the basis is sufficient to cover all of SU(4). In some embodiments, decompositions using a more general ‘super controlled’ basis U_{b}˜U_{d}(π/4,β_{b},0), for any β_{b }can be used. At least one embodiment also performs an expansion for restricted target unitaries U_{t}˜U_{d}(α_{t},β_{t},0), γ_{t}=0 for any α_{t}, β_{t}.
In this example, all of the above expansions are exact so that the constructed unitary U_{c }satisfies:
F_{avg}(U_{t}, U_{c})=1, (7)
In addition, eq. (5) of Section II also can be used by some embodiments to find the average gate fidelity due to approximating U_{t }by fewer uses of the basis gate than is necessary for exact expansion. For example, in some embodiments, for an arbitrary target with 0 applications of U_{b}, the following equation can be used:
U_{k}^{(0)}=(K_{l,1}^{l}⊗K_{l,2}^{r})(K_{l,2}^{l}⊗K_{l,2}^{r}), (8a)
F_{avg}^{(0)}=[4+16 cos^{2}(α_{t})cos^{2}(β_{t})cos^{2}(γ_{t})+16 sin^{2}(α_{t})sin^{2}(β_{t})sin^{2}(γ_{t})]/20. (8b)
With reference to
The system memory 616 can also include volatile memory 620 and nonvolatile memory 622. The basic input/output system (BIOS), containing the basic routines to transfer information between elements within the computer 612, such as during startup, is stored in nonvolatile memory 622. Computer 612 can also include removable/nonremovable, volatile/nonvolatile computer storage media.
System applications 630 take advantage of the management of resources by operating system 628 through program modules 632 and program data 634, e.g., stored either in system memory 616 or on disk storage 624. It is to be appreciated that this disclosure can be implemented with various operating systems or combinations of operating systems. A user enters commands or information into the computer 612 through input device(s) 636. Input devices 636 include, but are not limited to, a pointing device such as a mouse, trackball, stylus, touch pad, keyboard, microphone, joystick, game pad, satellite dish, scanner, TV tuner card, digital camera, digital video camera, web camera, and the like. These and other input devices connect to the processing unit 614 through the system bus 618 via interface port(s) 638. Interface port(s) 638 include, for example, a serial port, a parallel port, a game port, and a universal serial bus (USB). Output device(s) 640 use some of the same type of ports as input device(s) 636. Thus, for example, a USB port can be used to provide input to computer 612, and to output information from computer 612 to an output device 640. Output adapter 642 is provided to illustrate that there are some output devices 640 like monitors, speakers, and printers, among other output devices 640, which require special adapters. The output adapters 642 include, by way of illustration and not limitation, video and sound cards that provide a means of connection between the output device 640 and the system bus 618. It should be noted that other devices and/or systems of devices provide both input and output capabilities such as remote computer(s) 644.
Computer 612 can operate in a networked environment using logical connections to one or more remote computers, such as remote computer(s) 644. The remote computer(s) 644 can be a computer, a server, a router, a network PC, a workstation, a microprocessor based appliance, a peer device or other common network node and the like, and typically can also include many or all of the elements described relative to computer 612. For purposes of brevity, only a memory storage device 646 is illustrated with remote computer(s) 644. Remote computer(s) 644 is logically connected to computer 612 through a network interface 648 and then physically connected via communication connection 650. Network interface 648 encompasses wire and/or wireless communication networks such as localarea networks (LAN), widearea networks (WAN), cellular networks, etc. LAN technologies include Fiber Distributed Data Interface (FDDI), Copper Distributed Data Interface (CDDI), Ethernet, Token Ring and the like. WAN technologies include, but are not limited to, pointtopoint links, circuit switching networks like Integrated Services Digital Networks (ISDN) and variations thereon, packet switching networks, and Digital Subscriber Lines (DSL). Communication connection(s) 650 refers to the hardware/software employed to connect the network interface 648 to the system bus 618. While communication connection 650 is shown for illustrative clarity inside computer 612, it can also be external to computer 612. The hardware/software for connection to the network interface 648 can also include, for exemplary purposes only, internal and external technologies such as, modems including regular telephone grade modems, cable modems and DSL modems, ISDN adapters, and Ethernet cards.
The present invention can be a system, a method, an apparatus and/or a computer program product at any possible technical detail level of integration. The computer program product can include a computer readable storage medium (or media) having computer readable program instructions thereon for causing a processor to carry out aspects of the present invention. The computer readable storage medium can be a tangible device that can retain and store instructions for use by an instruction execution device. The computer readable storage medium can be, for example, but is not limited to, an electronic storage device, a magnetic storage device, an optical storage device, an electromagnetic storage device, a semiconductor storage device, or any suitable combination of the foregoing. A nonexhaustive list of more specific examples of the computer readable storage medium can also include the following: a portable computer diskette, a hard disk, a random access memory (RAM), a readonly memory (ROM), an erasable programmable readonly memory (EPROM or Flash memory), a static random access memory (SRAM), a portable compact disc readonly memory (CDROM), a digital versatile disk (DVD), a memory stick, a floppy disk, a mechanically encoded device such as punchcards or raised structures in a groove having instructions recorded thereon, and any suitable combination of the foregoing. A computer readable storage medium, as used herein, is not to be construed as being transitory signals per se, such as radio waves or other freely propagating electromagnetic waves, electromagnetic waves propagating through a waveguide or other transmission media (e.g., light pulses passing through a fiberoptic cable), or electrical signals transmitted through a wire.
Computer readable program instructions described herein can be downloaded to respective computing/processing devices from a computer readable storage medium or to an external computer or external storage device via a network, for example, the Internet, a local area network, a wide area network and/or a wireless network. The network can comprise copper transmission cables, optical transmission fibers, wireless transmission, routers, firewalls, switches, gateway computers and/or edge servers. A network adapter card or network interface in each computing/processing device receives computer readable program instructions from the network and forwards the computer readable program instructions for storage in a computer readable storage medium within the respective computing/processing device. Computer readable program instructions for carrying out operations of the present invention can be assembler instructions, instructionsetarchitecture (ISA) instructions, machine instructions, machine dependent instructions, microcode, firmware instructions, statesetting data, configuration data for integrated circuitry, or either source code or object code written in any combination of one or more programming languages, including an object oriented programming language such as Smalltalk, C++, or the like, and procedural programming languages, such as the “C” programming language or similar programming languages. The computer readable program instructions can execute entirely on the user'"'"'s computer, partly on the user'"'"'s computer, as a standalone software package, partly on the user'"'"'s computer and partly on a remote computer or entirely on the remote computer or server. In the latter scenario, the remote computer can be connected to the user'"'"'s computer through any type of network, including a local area network (LAN) or a wide area network (WAN), or the connection can be made to an external computer (for example, through the Internet using an Internet Service Provider). In one or more embodiments, electronic circuitry including, for example, programmable logic circuitry, fieldprogrammable gate arrays (FPGA), or programmable logic arrays (PLA) can execute the computer readable program instructions by utilizing state information of the computer readable program instructions to personalize the electronic circuitry, in order to perform aspects of the present invention.
Aspects of the present invention are described herein with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and/or block diagrams, and combinations of blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer readable program instructions. These computer readable program instructions can be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks. These computer readable program instructions can also be stored in a computer readable storage medium that can direct a computer, a programmable data processing apparatus, and/or other devices to function in a particular manner, such that the computer readable storage medium having instructions stored therein comprises an article of manufacture including instructions which implement aspects of the function/act specified in the flowchart and/or block diagram block or blocks. The computer readable program instructions can also be loaded onto a computer, other programmable data processing apparatus, or other device to cause a series of operational acts to be performed on the computer, other programmable apparatus or other device to produce a computer implemented process, such that the instructions which execute on the computer, other programmable apparatus, or other device implement the functions/acts specified in the flowchart and/or block diagram block or blocks.
The flowchart and block diagrams in the Figures illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to various embodiments of the present invention. In this regard, each block in the flowchart or block diagrams can represent a module, segment, or portion of instructions, which comprises one or more executable instructions for implementing the specified logical function(s). In some alternative implementations, the functions noted in the blocks can occur out of the order noted in the Figures. For example, two blocks shown in succession can, in fact, be executed substantially concurrently, or the blocks can sometimes be executed in the reverse order, depending upon the functionality involved. It will also be noted that each block of the block diagrams and/or flowchart illustration, and combinations of blocks in the block diagrams and/or flowchart illustration, can be implemented by special purpose hardwarebased systems that perform the specified functions or acts or carry out combinations of special purpose hardware and computer instructions.
While the subject matter has been described above in the general context of computerexecutable instructions of a computer program product that runs on a computer and/or computers, those skilled in the art will recognize that this disclosure also can or can be implemented in combination with other program modules. Generally, program modules include routines, programs, components, data structures, etc. that perform particular tasks and/or implement particular abstract data types. Moreover, those skilled in the art will appreciate that the inventive computerimplemented methods can be practiced with other computer system configurations, including singleprocessor or multiprocessor computer systems, minicomputing devices, mainframe computers, as well as computers, handheld computing devices (e.g., PDA, phone), microprocessorbased or programmable consumer or industrial electronics, and the like. The illustrated aspects can also be practiced in distributed computing environments in which tasks are performed by remote processing devices that are linked through a communications network. However, some, if not all aspects of this disclosure can be practiced on standalone computers. In a distributed computing environment, program modules can be located in both local and remote memory storage devices.
As used in this application, the terms “component,” “system,” “platform,” “interface,” and the like, can refer to and/or can include a computerrelated entity or an entity related to an operational machine with one or more specific functionalities. The entities disclosed herein can be either hardware, a combination of hardware and software, software, or software in execution. For example, a component can be, but is not limited to being, a process running on a processor, a processor, an object, an executable, a thread of execution, a program, and/or a computer. By way of illustration, both an application running on a server and the server can be a component. One or more components can reside within a process and/or thread of execution and a component can be localized on one computer and/or distributed between two or more computers. In another example, respective components can execute from various computer readable media having various data structures stored thereon. The components can communicate via local and/or remote processes such as in accordance with a signal having one or more data packets (e.g., data from one component interacting with another component in a local system, distributed system, and/or across a network such as the Internet with other systems via the signal). As another example, a component can be an apparatus with specific functionality provided by mechanical parts operated by electric or electronic circuitry, which is operated by a software or firmware application executed by a processor. In such a case, the processor can be internal or external to the apparatus and can execute at least a part of the software or firmware application. As yet another example, a component can be an apparatus that provides specific functionality through electronic components without mechanical parts, wherein the electronic components can include a processor or other means to execute software or firmware that confers at least in part the functionality of the electronic components. In an aspect, a component can emulate an electronic component via a virtual machine, e.g., within a cloud computing system.
In addition, the term “or” is intended to mean an inclusive “or” rather than an exclusive “or.” That is, unless specified otherwise, or clear from context, “X employs A or B” is intended to mean any of the natural inclusive permutations. That is, if X employs A; X employs B; or X employs both A and B, then “X employs A or B” is satisfied under any of the foregoing instances. Moreover, articles “a” and “an” as used in the subject specification and annexed drawings should generally be construed to mean “one or more” unless specified otherwise or clear from context to be directed to a singular form. As used herein, the terms “example” and/or “exemplary” are utilized to mean serving as an example, instance, or illustration. For the avoidance of doubt, the subject matter disclosed herein is not limited by such examples. In addition, any aspect or design described herein as an “example” and/or “exemplary” is not necessarily to be construed as preferred or advantageous over other aspects or designs, nor is it meant to preclude equivalent exemplary structures and techniques known to those of ordinary skill in the art.
As it is employed in the subject specification, the term “processor” can refer to substantially any computing processing unit or device comprising, but not limited to, singlecore processors; singleprocessors with software multithread execution capability; multicore processors; multicore processors with software multithread execution capability; multicore processors with hardware multithread technology; parallel platforms; and parallel platforms with distributed shared memory. Additionally, a processor can refer to an integrated circuit, an application specific integrated circuit (ASIC), a digital signal processor (DSP), a field programmable gate array (FPGA), a programmable logic controller (PLC), a complex programmable logic device (CPLD), a discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. Further, processors can exploit nanoscale architectures such as, but not limited to, molecular and quantumdot based transistors, switches and gates, in order to optimize space usage or enhance performance of user equipment. A processor can also be implemented as a combination of computing processing units. In this disclosure, terms such as “store,” “storage,” “data store,” data storage,” “database,” and substantially any other information storage component relevant to operation and functionality of a component are utilized to refer to “memory components,” entities embodied in a “memory,” or components comprising a memory. It is to be appreciated that memory and/or memory components described herein can be either volatile memory or nonvolatile memory, or can include both volatile and nonvolatile memory. By way of illustration, and not limitation, nonvolatile memory can include read only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable ROM (EEPROM), flash memory, or nonvolatile random access memory (RAM) (e.g., ferroelectric RAM (FeRAM). Volatile memory can include RAM, which can act as external cache memory, for example. By way of illustration and not limitation, RAM is available in many forms such as synchronous RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), double data rate SDRAM (DDR SDRAM), enhanced SDRAM (ESDRAM), Synchlink DRAM (SLDRAM), direct Rambus RAM (DRRAM), direct Rambus dynamic RAM (DRDRAM), and Rambus dynamic RAM (RDRAM). Additionally, the disclosed memory components of systems or computerimplemented methods herein are intended to include, without being limited to including, these and any other suitable types of memory.
What has been described above include mere examples of systems and computerimplemented methods. It is, of course, not possible to describe every conceivable combination of components or computerimplemented methods for purposes of describing this disclosure, but one of ordinary skill in the art can recognize that many further combinations and permutations of this disclosure are possible. Furthermore, to the extent that the terms “includes,” “has,” “possesses,” and the like are used in the detailed description, claims, appendices and drawings such terms are intended to be inclusive in a manner similar to the term “comprising” as “comprising” is interpreted when employed as a transitional word in a claim.
The descriptions of the various embodiments have been presented for purposes of illustration, but are not intended to be exhaustive or limited to the embodiments disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The terminology used herein was chosen to best explain the principles of the embodiments, the practical application or technical improvement over technologies found in the marketplace, or to enable others of ordinary skill in the art to understand the embodiments disclosed herein.