QUANTUM COMPUTER AND QUANTUM COMPUTING USING ISING MODEL

• US 20140200689A1
• Filed: 11/07/2013
• Published: 07/17/2014
• Est. Priority Date: 01/11/2013
• Status: Active Grant

• Current Assignee: Inter-University Research Institute Corporation National Institutes of Natural Sciences, Inter-university Research Institute Corporation Research Organization of Information and Systems, Board of Trustees of the Leland Stanford Junior University (Stanford University)
• Original Assignee: Inter-university Research Institute Corporation Research Organization of Information and Systems, Board of Trustees of the Leland Stanford Junior University (Stanford University)
• Inventors: Yamamoto, Yoshihisa, Utsunomiya, Shoko, Takata, Kenta, Wen, Kai
• Granted Patent: US 9,342,792 B2
• Time in Patent Office: Days
• US Class Current: 700/90
• CPC Class Codes: B82Y 10/00 Nanotechnology for information processing, storage or transmission, e.g. quantum computing or single electron logic
• CPC Class Codes: G06N 10/00 Quantum computing, i.e. information processing based on quantum-mechanical phenomena

Abstract

For each pair of a plurality of slave lasers B for which injection synchronization is performed by a master laser M, by controlling the intensity of light exchanged between two slave lasers B and an optical path length between the two slave lasers B using a slave-to-laser intensity control unit IA and an inter-slave laser optical path length control unit IP, the magnitude and the sign of pseudo ising interaction J_ij between the two slave lasers B are implemented. After the plurality of slave lasers B arrive at a steady state, by measuring relative values of the oscillation phases of the plurality of slave lasers B with respect to the oscillation phase of the master laser M by using an oscillation phase measuring unit PM, pseudo ising spins σ_i of the plurality of slave lasers B are measured.

Claims

1. A quantum computer using an ising model comprising:

a plurality of coherent oscillators that oscillate light having polarization polarized in a same direction determined in advance in correspondence with a plurality of sites of the ising model;

a master oscillator that performs injection synchronization for the plurality of coherent oscillators and oscillates the light having polarization polarized in the same direction determined in advance;

a master oscillator-to-coherent oscillator optical path unit that is arranged between the master oscillator and each one of the coherent oscillators;

an inter-coherent oscillator optical path unit that is arranged between two coherent oscillators for each pair of the plurality of the coherent oscillators;

an oscillation frequency control unit that is arranged in each master oscillator-to-coherent oscillator optical path unit and controls an oscillation frequency of each one of the coherent oscillators so as to be an oscillation frequency of the master oscillator;

an inter-coherent oscillator intensity control unit that is arranged in each inter-coherent oscillator optical path unit for each pair of the plurality of the coherent oscillators and implements a magnitude of pseudo ising interaction between two coherent oscillators by controlling an intensity of light exchanged between the two coherent oscillators;

an inter-coherent oscillator optical path length control unit that is arranged in each inter-coherent oscillator optical path unit for each pair of the plurality of the coherent oscillators and implements a sign of the pseudo ising interaction between two coherent oscillators by controlling an optical path length between the two coherent oscillators; and

an oscillation phase measuring unit that measures pseudo ising spins of the plurality of the coherent oscillators by measuring relative values of oscillation phases of the plurality of the coherent oscillators with respect to the oscillation phase of the master oscillator after the plurality of the coherent oscillators arrive at a steady state.

2. The quantum computer using an ising model according to claim 1, wherein each inter-coherent oscillator optical path length control unit implements the sign of pseudo ising interaction between two coherent oscillators by performing control such that an optical path length between the two coherent oscillators is a half-integer multiple or an integer multiple of an oscillation wavelength of the injection synchronization.

3. The quantum computer using an ising model according to claim 1, wherein the oscillation phase measuring unit determines that directions of pseudo ising spins of two coherent oscillators to be the same when oscillation phases of both the coherent oscillators lead before or lag behind the oscillation phase of the master oscillator for each pair of the plurality of the coherent oscillators and determines that the directions of the pseudo ising spins of two coherent oscillators to be different from each other when an oscillation phase of one coherent oscillator leads before the oscillation phase of the master oscillator and the oscillation phase of the other coherent oscillator lags behind the oscillation phase of the master oscillator for each pair of the plurality of the coherent oscillators.

4. The quantum computer using an ising model according to claim 1, further comprising:

a master oscillator-to-coherent oscillator intensity control unit that is arranged in each master oscillator-to-coherent oscillator optical path unit and implements the magnitude of pseudo Zeeman energy in each coherent oscillator by controlling the intensity of light injected into each coherent oscillator; and

a master oscillator-to-coherent oscillator phase control unit that is arranged in each master oscillator-to-coherent oscillator optical path unit and implements the sign of the pseudo Zeeman energy in each coherent oscillator by controlling the phase of light injected into each coherent oscillator.

5. The quantum computer using an ising model according to claim 4, wherein each master oscillator-to-coherent oscillator phase control unit implements the sign of the pseudo Zeeman energy in each coherent oscillator by controlling lead or lag of an injection phase for each coherent oscillator with respect to the oscillation phase of the master oscillator.

6. The quantum computer using an ising model according to claim 1, wherein each oscillation frequency control unit controls the oscillation frequency of each coherent oscillator so as to be the oscillation frequency of the master oscillator by performing control such that an interference intensity of oscillated light of each coherent oscillator and oscillated light of the master oscillator is an extreme value with respect to a change in the oscillation frequency of each coherent oscillator.

7. The quantum computer using an ising model according to claim 1, wherein each inter-coherent oscillator optical path length control unit controls an optical path length between two coherent oscillators so as to be a half-integer multiple or an integer multiple of an oscillation wavelength of the injection synchronization by performing control such that an interference intensity of oscillated light of the two coherent oscillators is an extreme value with respect to a change in the optical path length between the two coherent oscillators.

8. The quantum computer using an ising model according to claim 1, wherein control of the oscillation frequency of each coherent oscillator in each oscillation frequency control unit, control of the optical path length between two coherent oscillators in each inter-coherent oscillator optical path length control unit, and measurement of the pseudo ising spins of the plurality of the coherent oscillators in the oscillation phase measuring unit are performed in the mentioned order.

9. The quantum computer using an ising model according to claim 1, further comprising a pumping current control unit that performs gradual increase control of pumping currents of two coherent oscillators for the two coherent oscillators performing pseudo ising interaction through each inter-coherent oscillator optical path unit in a state in which the magnitude and the sign of the pseudo ising intersection between the two coherent oscillators are implemented to be fixed values and performs fixing control of the pumping currents of the two coherent oscillators at a time point when the plurality of the coherent oscillators arrive at one integrally oscillation mode for the first time,

wherein the oscillation phase measuring unit, after the plurality of the coherent oscillators arrive at one integrally oscillation mode so as to arrive at a steady state, measures the pseudo ising spins of the plurality of the coherent oscillators by measuring relative values of the oscillation phases of the plurality of the coherent oscillators with respect to the oscillation phase of the master oscillator.

10. The quantum computer using an ising model according to claim 1, further comprising an adjacent ising spin direction fixing unit that is arranged in each master oscillator-to-coherent oscillator optical path unit, and, for two coherent oscillators performing pseudo ising interaction through each inter-coherent oscillator optical path unit, by controlling the intensity and the phase of light injected into the two coherent oscillators when relative values of the oscillation phases of the two coherent oscillators with respect to the oscillation phase of the master oscillator are not measured to be meaningful, fixes the directions of pseudo ising spins of the two coherent oscillators to be different from each other when the sign of the pseudo ising interaction between the two coherent oscillators is implemented to be positive and fixes the directions of the pseudo ising spins of the two coherent oscillators to be the same when the sign of the pseudo ising interaction between the two coherent oscillators is implemented to be negative.

11. The quantum computer using an ising model according to claim 10, further comprising a peripheral ising spin direction fixing unit that is arranged in each master oscillator-to-coherent oscillator optical path unit, and, for two coherent oscillators performing pseudo ising interaction through each inter-coherent oscillator optical path unit, by controlling the intensity and the phase of light injected into an adjacent coherent oscillator performing pseudo ising interaction with the two coherent oscillators through another inter-coherent oscillator optical path unit when relative values of the oscillation phases of the two coherent oscillators with respect to the oscillation phase of the master oscillator are not measured to be meaningful, fixes the direction of the pseudo ising spin of the adjacent coherent oscillator to a direction of a current time point during computation.

12. The quantum computer using an ising model according to claim 1, wherein a delay time of the pseudo ising interaction between two coherent oscillators performing pseudo ising interaction through each inter-coherent oscillator optical path unit is shorter than the reciprocal of the injection locking width in the master oscillator and the two coherent oscillators.

13. The quantum computer using an ising model according to claim 1, wherein the plurality of the coherent oscillators are a plurality of slave lasers.

14. The quantum computer using an ising model according to claim 1, wherein the plurality of the coherent oscillators are a plurality of Bose-Einstein condensates.

15. The quantum computer using an ising model according to claim 1, wherein the master oscillator is a master laser.

16. A quantum computing using an ising model comprising:

an oscillation starting step of starting oscillation of a plurality of coherent oscillators that oscillate light having polarization polarized in a same direction determined in advance in correspondence with a plurality of sites of the ising model and of starting oscillation of a master oscillator that performs injection synchronization for the plurality of coherent oscillators and oscillates light having polarization polarized in the same direction determined in advance;

an oscillation frequency control step of controlling an oscillation frequency of each one of the coherent oscillators so as to be an oscillation frequency of the master oscillator;

an inter-coherent oscillator intensity optical path length control step of implementing the magnitude of pseudo ising interaction between two coherent oscillators by controlling the intensity of light exchanged between the two coherent oscillators for each pair of the plurality of the coherent oscillators and of implementing the sign of the pseudo ising interaction between two coherent oscillators by controlling an optical path length between the two coherent oscillators for each pair of the plurality of the coherent oscillators; and

an oscillation phase measurement step of measuring pseudo ising spins of the plurality of the coherent oscillators by measuring relative values of oscillation phases of the plurality of the coherent oscillators with respect to the oscillation phase of the master oscillator after the plurality of the coherent oscillators arrive at a steady state.

17. The quantum computing using an ising model according to claim 16, wherein the inter-coherent oscillator intensity optical path length control step implements the sign of pseudo ising interaction between two coherent oscillators by performing control such that the optical path length between the two coherent oscillators is a half-integer multiple or an integer multiple of an oscillation wavelength of the injection synchronization.

18. The quantum computing using an ising model according to claim 16, wherein, in the oscillation phase measurement step, directions of pseudo ising spins of two coherent oscillators are determined to be the same when oscillation phases of both the coherent oscillators lead before or lag behind the oscillation phase of the master oscillator for each pair of the plurality of the coherent oscillators, and the directions of the pseudo ising spins of two coherent oscillators are determined to be different from each other when an oscillation phase of one coherent oscillator leads before the oscillation phase of the master oscillator, and the oscillation phase of the other coherent oscillator lags behind the oscillation phase of the master oscillator.

19. The quantum computing using an ising model according to claim 16, further comprising of a master oscillator-to-coherent oscillator intensity phase control step of implementing the magnitude of pseudo Zeeman energy in each coherent oscillator by controlling the intensity of light injected into each coherent oscillator and of implementing the sign of the pseudo Zeeman energy in each coherent oscillator by controlling the phase of light injected into each coherent oscillator, in parallel with the inter-coherent oscillator intensity optical path control step.

20. The quantum computing using an ising model according to claim 19, wherein, in the master oscillator-to-coherent oscillator intensity phase control step, the sign of the pseudo Zeeman energy in each coherent oscillator is implemented by controlling lead or lag of an injection phase for each coherent oscillator with respect to the oscillation phase of the master oscillator.