We show that quantum diffusion near a quantum critical point can provide an efficient mechanism of quantum annealing. It is based on the diffusion-mediated recombination of excitations in open systems far from thermal equilibrium. We find that, for an Ising spin chain coupled to a bosonic bath and driven by a monotonically decreasing transverse field, excitation diffusion sharply slows down below the quantum critical region. This leads to spatial correlations and effective freezing of the excitation density. Still, obtaining an approximate solution of an optimization problem via the diffusion-mediated quantum annealing can be faster than via closed-system quantum annealing or Glauber dynamics.We show that quantum diffusion near a quantum critical point can provide an efficient mechanism of quantum annealing. It is based on the diffusion-mediated recombination of excitations in open systems far from thermal equilibrium. We find that, for an Ising spin chain coupled to a bosonic bath and driven by a monotonically decreasing transverse field, excitation diffusion sharply slows down below the quantum critical region. This leads to spatial correlations and effective freezing of the excitation density. Still, obtaining an approximate solution of an optimization problem via the diffusion-mediated quantum annealing can be faster than via closed-system quantum annealing or Glauber dynamics.

arXiv:1511.02581Physical Review LettersFeb 10, 201734 citations

Recent progress of quantum annealing

Sei Suzuki

AIP conference proceedingsJan 1, 20150 citations

Harnessing Environment-Mediated Crosstalk: Mutual Performance Enhancement in Parallel Quantum Annealing

Jargalsaikhan Artag, Koki Awaya, Takumi Kanezashi +3 more

Parallel Quantum Annealing (PQA) is a technique to improve computational throughput by running multiple independent problems concurrently. However, the concurrent execution of independent problems on a shared physical device gives rise to the possibility of unintended crosstalk mediated by the hardware environment. This work investigates a novel strategy to not only probe but actively harness these interactions. We hypothesize that applying relative time offsets to the annealing schedules of parallel problems can control these environment-mediated dynamics. To show this, we executed two independent ferromagnetic Ising chains (up to $N=500$ qubits) in parallel on a D-Wave quantum annealer, systematically varying the schedule offset of one chain relative to the other. Our experimental results reveal a strong, non-monotonic dependence of the Ground State Probability (GSP) on the applied offset. Most significantly, we discovered non-zero offset regimes where both concurrently running problems achieved higher GSPs than their respective single-run baselines. This counter-intuitive finding of mutual performance enhancement suggests a controllable, cooperative dynamic mediated by the shared quantum environment. This reframes environmental crosstalk from a simple source of error into a potential resource, opening new avenues for schedule optimization and for probing the complex open-system dynamics of near-term quantum devices.Parallel Quantum Annealing (PQA) is a technique to improve computational throughput by running multiple independent problems concurrently. However, the concurrent execution of independent problems on a shared physical device gives rise to the possibility of unintended crosstalk mediated by the hardware environment. This work investigates a novel strategy to not only probe but actively harness these interactions. We hypothesize that applying relative time offsets to the annealing schedules of parallel problems can control these environment-mediated dynamics. To show this, we executed two independent ferromagnetic Ising chains (up to$N=500$qubits) in parallel on a D-Wave quantum annealer, systematically varying the schedule offset of one chain relative to the other. Our experimental results reveal a strong, non-monotonic dependence of the Ground State Probability (GSP) on the applied offset. Most significantly, we discovered non-zero offset regimes where both concurrently running problems achieved higher GSPs than their respective single-run baselines. This counter-intuitive finding of mutual performance enhancement suggests a controllable, cooperative dynamic mediated by the shared quantum environment. This reframes environmental crosstalk from a simple source of error into a potential resource, opening new avenues for schedule optimization and for probing the complex open-system dynamics of near-term quantum devices.

IEEE International Conference on Quantum Computing and Engineering (QCE)Aug 30, 20250 citations

Experimental signatures of quantum annealing

Sergio Boixo

Bulletin of the American Physical SocietyMar 18, 20135 citations

A quantum diffusion network

George Kesidis

Wong's diffusion network is a stochastic, zero-input Hopfield network with a Gibbs stationary distribution over a bounded, connected continuum. Previously, logarithmic thermal annealing was demonstrated for the diffusion network and digital versions of it were studied and applied to imaging. Recently, "quantum" annealed Markov chains have garnered significant attention because of their improved performance over "pure" thermal annealing. In this note, a joint quantum and thermal version of Wong's diffusion network is described and its convergence properties are studied. Different choices for "auxiliary" functions are discussed, including those of the kinetic type previously associated with quantum annealing.Wong's diffusion network is a stochastic, zero-input Hopfield network with a Gibbs stationary distribution over a bounded, connected continuum. Previously, logarithmic thermal annealing was demonstrated for the diffusion network and digital versions of it were studied and applied to imaging. Recently, "quantum" annealed Markov chains have garnered significant attention because of their improved performance over "pure" thermal annealing. In this note, a joint quantum and thermal version of Wong's diffusion network is described and its convergence properties are studied. Different choices for "auxiliary" functions are discussed, including those of the kinetic type previously associated with quantum annealing.

arXiv:0908.1597Aug 11, 20091 citation

Assessing the Quantum in Quantum Annealing

Wade DeGottardi, David Ferguson, С. А. Новиков +2 more

Bulletin of the American Physical SocietyMar 7, 20190 citations

N=500

qubits) in parallel on a D-Wave quantum annealer, systematically varying the schedule offset of one chain relative to the other. Our experimental results reveal a strong, non-monotonic dependence of the Ground State Probability (GSP) on the applied offset. Most significantly, we discovered non-zero offset regimes where both concurrently running problems achieved higher GSPs than their respective single-run baselines. This counter-intuitive finding of mutual performance enhancement suggests a controllable, cooperative dynamic mediated by the shared quantum environment. This reframes environmental crosstalk from a simple source of error into a potential resource, opening new avenues for schedule optimization and for probing the complex open-system dynamics of near-term quantum devices.