Ring oscillator-based Ising machine system

Patent metadata

Field	Value
Publication number	US-11545963-B1
Application number	US-202117540985-A
Country	US
Kind code	B1
Filing date	Dec 2, 2021
Priority date	Dec 2, 2021
Publication date	Jan 3, 2023
Grant date	Jan 3, 2023

Abstract

One example includes an Ising machine system. The system includes a plurality of ring oscillators that are each configured to propagate an oscillation signal. Each of the ring oscillators can be cross-coupled with at least one other of the ring oscillators via a respective one of the oscillation signals to provide a respective phase coupling between the respective cross-coupled ring oscillators. The system also includes an Ising machine controller configured to generate control signals corresponding to parameters of an Ising problem and including a plurality of delay selection signals. The Ising machine controller can provide at least one of the delay selection signals to each of the ring oscillators. The delay selection signal can be configured to set a variable propagation delay of the ring oscillator to control the relative phase coupling of each of the ring oscillators to each of the at least one other of the ring oscillators.

First claim

What is claimed is:

1. An Ising machine system comprising:
a plurality of ring oscillators that are each configured to propagate an oscillation signal, each of the ring oscillators being cross-coupled with at least one other of the ring oscillators via a respective one of the oscillation signals to provide a respective phase coupling between the respective cross-coupled ring oscillators; and
an Ising machine controller configured to generate a plurality of control signals corresponding to parameters of an Ising problem, the control signals comprising a plurality of delay selection signals, the Ising machine controller providing at least one of the delay selection signals to each of the ring oscillators, the delay selection signal being configured to set a variable propagation delay of the ring oscillator to control the relative phase coupling of each of the ring oscillators to each of the at least one other of the ring oscillators.

2. The system of claim 1 , wherein each of the ring oscillators comprises a plurality of coupling stages, each of the coupling stages being configured to receive a set of the control signals comprising a respective one of the delay selection signals, such that each of the ring oscillators has a net oscillation period of the respective oscillation signal at a given instant that is set based on the delay selection signal provided to each of the coupling stages of the respective one of the ring oscillators.

3. The system of claim 2 , wherein each of the ring oscillators is cross-coupled with the at least one other of the ring oscillators via the respective one of the oscillation signals provided from one of the respective coupling stages associated with the respective one of the ring oscillators and received from a respective one of the coupling stages associated with the respective at least one other of the ring oscillators to provide the respective phase coupling between the respective cross-coupled ring oscillators.

4. The system of claim 2 , wherein each set of the control signals comprises an enable signal that is provided to each of coupling stages of the respective one of the ring oscillators, the enable signal being configured to select between a nominal propagation delay and the variable propagation delay of a respective one of the coupling stages.

5. The system of claim 2 , wherein each set of the control signals comprises a cross-coupling polarity signal that is provided to each of coupling stages of the respective one of the ring oscillators, the cross-coupling polarity signal being configured to select between phase alignment and phase anti-alignment of the ring oscillator relative to the other cross-coupled at least one of the ring oscillators associated with the respective one of the coupling stages.

6. The system of claim 2 , wherein each of the coupling stages comprise a first digital-to-time converter and a second digital-to-time converter that are each configured to receive the delay selection signal, wherein each of the coupling stages is configured to provide one of a fast oscillation in which the oscillation signal passes through neither of the first or second digital-to-time converters, a nominal oscillation in which the oscillation signal passes through the first digital-to-time converter but not the second digital-to-time converter, and a slow oscillation in which the oscillation signal passes through both of the first or second digital-to-time converters.

7. The system of claim 2 , wherein each of the coupling stages comprises:
a delay register that is configured to provide a plurality of copies of the oscillation signal that are each delayed by a different amount; and
at least one multiplexer configured to select one of the copies of the oscillation signal based on the delay selection signal.

8. The system of claim 2 , wherein each set of the control signals comprises a clock signal having a predetermined frequency to provide phase coupling of the respective one of the ring oscillators to the clock signal.

9. The system of claim 2 , wherein each set of the control signals comprises a simulated noise signal having a simulated noise signal characteristic to provide phase coupling of the respective one of the ring oscillators to simulated noise.

10. The system of claim 9 , wherein the simulated noise signal characteristic comprises one of a pulse frequency and a pulse width to simulate an analog characteristic associated with the simulated noise signal.

11. The system of claim 1 , wherein each of the ring oscillators are fabricated as complementary metal-oxide semiconductor (CMOS) ring oscillators.

12. A method for solving an Ising problem, the method comprising:
providing an Ising machine system comprising a plurality of complementary metal-oxide semiconductor (CMOS) ring oscillators that are each configured to propagate an oscillation signal, each of the CMOS ring oscillators being cross-coupled with at least one other of the CMOS ring oscillators via a respective one of the oscillation signals to provide a respective phase coupling between the respective cross-coupled CMOS ring oscillators; and
providing a set of control signals corresponding to parameters of an Ising problem to each of the CMOS ring oscillators, each of the sets of control signals comprising a delay selection signal configured to set a variable propagation delay of the respective one of the CMOS ring oscillators to control the relative phase coupling of each of the CMOS ring oscillators to each of the at least one other of the CMOS ring oscillators.

13. The method of claim 12 , wherein providing the set of control signals comprises providing the set of control signals to each of a plurality of coupling stages of each of the CMOS ring oscillators, such that each of the CMOS ring oscillators has an oscillation period of the respective oscillation signal that is set based on the delay selection signal provided to each of coupling stages of the respective one of the CMOS ring oscillators.

14. The method of claim 13 , wherein providing the set of control signals comprises providing an enable signal to each of a plurality of coupling stages of each of the CMOS ring oscillators, the enable signal being configured to select between a nominal propagation delay and the variable propagation delay of a respective one of the coupling stages.

15. The method of claim 13 , wherein providing the set of control signals comprises providing a cross-coupling polarity signal to each of a plurality of coupling stages of each of the CMOS ring oscillators, the cross-coupling polarity signal being configured to select between phase alignment and phase anti-alignment of the CMOS ring oscillator relative to the other cross-coupled at least one of the CMOS ring oscillators associated with the respective one of the coupling stages.

16. The method of claim 13 , wherein providing the set of control signals comprises providing at least one of a clock signal and a simulated noise signal to each of a plurality of coupling stages of each of the CMOS ring oscillators, wherein the clock signal has a predetermined frequency to provide phase coupling of the respective one of the CMOS ring oscillators to the clock signal, wherein the simulated noise signal has a simulated noise signal characteristic to provide phase coupling of the respective one of the CMOS ring oscillators to simulated noise.

17. An Ising machine system comprising:
a plurality of ring oscillators that are each configured to propagate an oscillation signal, each of the ring oscillators comprises a plurality of coupling stages, each of the ring o

Assignees

• Zick Kenneth M
• Northrop Grumman Systems Corp

Inventors

• Zick Kenneth M

Classifications

• G06F17/11

  for solving equations {, e.g. nonlinear equations, general mathematical optimization problems (optimization specially adapted for a specific administrative, business or logistic context G06Q10/04)} · CPC title

• H03K3/86

  Generating pulses by means of delay lines and not covered by the preceding subgroups · CPC title

• H03K3/0315

  Ring oscillators · CPC title

• G06N5/01 Primary

  Dynamic search techniques; Heuristics; Dynamic trees; Branch-and-bound · CPC title

• G06N7/01

  Probabilistic graphical models, e.g. probabilistic networks · CPC title