PROVIDING CONTROLLED PULSES FOR QUANTUM COMPUTING

• US 20170076787A1
• Filed: 09/13/2015
• Published: 03/16/2017
• Est. Priority Date: 09/13/2015
• Status: Active Grant

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Frank, David J.
• Granted Patent: US 9,847,121 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G06N 10/00 Quantum computing, i.e. information processing based on quantum-mechanical phenomena
• CPC Class Codes: G11C 11/44 using super-conductive elements, e.g. cryotron

Abstract

A quantum mechanical radio frequency (RF) signaling system includes a transmission line that receives and conducts an RF pulse signal operating at a radio frequency, a first qubit having a quantum mechanical state that is a linear combination of at least two quantum mechanical eigenstates, and a first network of reactive electrical components having an input that is coupled to the transmission line for receiving the RF pulse signal and an output that is coupled to the first qubit. The first network of reactive electrical components attenuates the amplitude of the RF pulse signal and produces a first attenuated RF pulse signal that is applied to the first qubit. The first attenuated RF pulse signal operates at the radio frequency and has a first attenuated amplitude that causes a predefined change in the linear combination of at least two quantum mechanical eigenstates within the first qubit.

Claims

1. A quantum mechanical radio frequency (RF) signaling system comprising:

a transmission line that receives and conducts an RF pulse signal operating at a radio frequency;

a first qubit having a quantum mechanical state that is a linear combination of at least two quantum mechanical eigenstates; and

a first network of reactive electrical components having an input coupled to the transmission line for receiving the RF pulse signal and an output coupled to the first qubit, wherein the first network of reactive electrical components attenuates the amplitude of the RF pulse signal and produces a first attenuated RF pulse signal that is applied to the first qubit, the first attenuated RF pulse signal operating at the radio frequency and having a first attenuated amplitude that cause a predefined change in the linear combination of at least two quantum mechanical eigenstates within the first qubit, wherein the first network of reactive electrical components include an adjustable reactance for varying an attenuation associated with the first attenuated amplitude.

2. The system of claim 1, further comprising:

a second qubit substantially identical to the first qubit, the second qubit having a quantum mechanical state that is a linear combination of at least two quantum mechanical eigenstates; and

a second network of reactive electrical components having an input coupled to the transmission line for receiving the RF pulse signal and an output coupled to the second qubit, wherein the second network of reactive electrical components attenuates the amplitude of the RF pulse signal and produces a second attenuated RF pulse signal that is applied to the second qubit, the second attenuated RF pulse signal operating at the radio frequency and having a second attenuated amplitude that cause the predefined change in the linear combination of at least two quantum mechanical eigenstates within the second qubit,

wherein the first attenuated amplitude and the second attenuated amplitude compensate for differences in reactive component tolerances between the first network of reactive electrical components and the second network of reactive electrical components.

3. The system of claim 2, wherein the first qubit is coupled through a reactive electrical network to the second qubit.

4. The system of claim 1, wherein the first network of reactive electrical components comprises a first controllable reactive component to attenuate, in a controlled manner, the amplitude of the first attenuated RF pulse signal.

5. The system of claim 4, wherein the ratio of the RF pulse signal to the first attenuated RF pulse signal is about 10-100.

6. The system of claim 4, wherein the first network of reactive electrical components comprise:

a first input reactive component coupled to and in series with the first controllable reactive component, the first input reactive component having a first terminal that is coupled to the transmission line for receiving the RF pulse signal and a second terminal that is coupled to the first controllable reactive component.

7. The system of claim 6,

wherein the first controllable reactive component comprises a first plurality of parallel capacitor devices each having a switch connected in series, the first plurality of parallel capacitor devices having a terminal coupled to the second terminal of the first input reactive component and a terminal coupled to ground, and

wherein upon actuation of the switch to a closed position, a corresponding capacitor device associated with the first plurality of parallel capacitor devices that is in series with the switch remains within the first plurality of parallel capacitor devices, and

wherein upon actuation of the switch to an open position, the corresponding capacitor device associated with the first plurality of parallel capacitor devices that is in series with the switch is removed from the first plurality of parallel capacitor devices.

8. The system of claim 2, wherein the second network of reactive electrical components comprises a second controllable reactive component to attenuate, in a controlled manner, the amplitude of the second attenuated RF pulse signal.

9. The system of claim 8, wherein the ratio of the RF pulse signal to the second attenuated pulse RF signal is about 10-100.

10. The system of claim 8, wherein the second network of reactive electrical components comprise:

a second input reactive component coupled to and in series with the second controllable reactive component, the second input reactive component having a first terminal that is coupled to the transmission line for receiving the RF pulse signal and a second terminal that is coupled to the second controllable reactive component.

11. The system of claim 10,

wherein the second controllable reactive component comprises a second plurality of parallel capacitor devices each having a switch connected in series, the second plurality of parallel capacitor devices having a terminal coupled to the second terminal of the second input reactive component and a terminal coupled to ground, and

wherein upon actuation of the switch to a closed position, a corresponding capacitor device associated with the second plurality of parallel capacitor devices that is in series with the switch remains within the second plurality of parallel capacitor devices, and

wherein upon actuation of the switch to an open position, the corresponding capacitor device associated with the second plurality of parallel capacitor devices is removed from the second plurality of parallel capacitor devices.

12. The system of claim 2, wherein the RF pulse signal comprises pulse periods of about 10-500 nanoseconds, and wherein the operating frequency within each of the pulse periods comprises a frequency of about 1-10 GHz.

13. The system of claim 1, further comprising:

a first switch unit having an input and an output, wherein the input of the first switch unit is coupled to the first network of reactive electrical components; and

a first output-stage network of reactive electrical components having an input and an output, wherein the input of the first output-stage network of reactive electrical components is coupled to the output of the first switch unit, and wherein the output of the first output-stage network of reactive electrical components is coupled to the first qubit.

14. The system of claim 13, wherein the first switch unit comprises a first switch device that controls an electrical connection for coupling the first attenuated RF pulse signal received from the first network of reactive electrical components to the first output-stage network of reactive electrical components, and wherein upon actuation of the first switch device to a closed position, the first attenuated RF pulse signal is further attenuated by the first output-stage network of reactive electrical components and causes the predefined change in the linear combination of at least two quantum mechanical eigenstates within the first qubit based on the applied radio frequency, and wherein upon actuation of the first switch device to an open position the first qubit remains in a previous established linear combination of at least two quantum mechanical eigenstates within the first qubit.

15. The system of claim 2, wherein the first qubit comprises a first transmon and the second qubit comprises a second transmon.

16. The system of claim 2, further comprising:

a second switch unit having an input and an output, wherein the input of the second switch unit is coupled to the second network of discrete reactive electrical components; and

a second output-stage network of reactive electrical components having an input and an output, wherein the input of the second output-stage network of reactive electrical components is coupled to the output of the second switch unit and the output of the second output-stage network of reactive electrical components is coupled to the second qubit.

17. The system of claim 16, wherein the second switch unit comprises a second switch device that controls an electrical connection for coupling the second attenuated RF pulse signal received from the second network of reactive electrical components to the second output-stage network of reactive electrical components, and wherein upon actuation of the second switch device to a closed position the second attenuated RF pulse signal is further attenuated by the second output-stage network of reactive electrical components and causes the predefined change in the linear combination of at least two quantum mechanical eigenstates within the second qubit based on the applied radio frequency, and wherein upon actuation of the second switch device to an open position the second qubit remains in a previous established linear combination of at least two quantum mechanical eigenstates within the second qubit.

18. A computer system for providing radio frequency (RF) signalling over a transmission line to a plurality of qubits coupled to the transmission line in a quantum mechanical computer system, the computer system comprising:

one or more processors, one or more computer-readable memories, one or more computer-readable tangible storage devices, and program instructions stored on at least one of the one or more storage devices for execution by at least one of the one or more processors via at least one of the one or more memories, wherein the computer system is capable of performing a method comprising;

applying an RF pulse signal operating at a radio frequency to the transmission line;

attenuating, using a first network of reactive electrical components, the amplitude of the applied RF pulse signal received from the transmission line to generate a first attenuated RF pulse signal operating at the radio frequency and having a first attenuated amplitude;

attenuating, using a second network of reactive electrical components, the amplitude of the applied RF pulse signal received from the transmission line to generate a second attenuated RF pulse signal operating at the radio frequency and having a second attenuated amplitude;

applying the first attenuated RF pulse signal to the first qubit and causing, based on the first attenuated amplitude, a predefined change in a linear combination of at least two quantum mechanical eigenstates within the first qubit, and

applying the second attenuated RF pulse signal to the second qubit and causing, based on the second attenuated amplitude, the predefined change in the linear combination of at least two quantum mechanical eigenstates within the second qubit,

wherein the first attenuated signal and the second attenuated signal compensate for differences in reactive component tolerances between the first network of reactive electrical components and the second network of reactive electrical components.

19. The computer system of claim 18, wherein

the applying of the first attenuated RF pulse signal and causing the predefined change in the linear combination of at least two quantum mechanical eigenstates within the first qubit comprises closing a first switch located in a path between the first network of discrete reactive electrical components and the first qubit, and

wherein the applying of the second attenuated RF pulse signal and causing the predefined change in the linear combination of at least two quantum mechanical eigenstates within the second qubit comprises closing a second switch located in a path between the second network of discrete reactive electrical components and the second qubit.

20. A quantum mechanical radio frequency (RF) signalling system comprising:

a first qubit having a first input;

a second qubit having a second input;

a reactive element coupled between the first input of the first qubit and the second input of the second qubit;

a first transmission line that receives and conducts a first RF pulse signal having a first radio frequency;

a second transmission line that receives and conducts a second RF pulse signal having a second radio frequency;

a first network of reactive electrical components having an input coupled to the first transmission line for receiving the first RF pulse signal and an output coupled to the first qubit, wherein the first network of reactive electrical components attenuates the amplitude of the first RF pulse signal and produces a first attenuated RF pulse signal that is applied to the first qubit, the first attenuated RF pulse signal operating at the first radio frequency and having a first attenuated amplitude that causes a predefined change in a linear combination of at least two quantum mechanical eigenstates within the first qubit; and

a second network of reactive electrical components having an input coupled to the second transmission line for receiving the second RF pulse signal and an output coupled to the first qubit, wherein the second network of reactive electrical components attenuates the amplitude of the second RF pulse signal and produces a second attenuated RF pulse signal that is applied to the first qubit and coupled to the second qubit via the coupling element, the second attenuated RF pulse signal operating at the second radio frequency and having a second attenuated amplitude that causes a quantum mechanical entanglement between the first qubit and the second qubit.