Experimental test of search range in quantum annealing

Chancellor, Nicholas; Kendon, Viv

doi:10.1103/physreva.104.012604

Cited by 9 publications

(8 citation statements)

References 31 publications

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“…Therefore thermalization in a quantum system is seen to be of some computational use, as has been seen in other literature [24][25][26][27][28]. However, we see that on the time scales tested that thermalization in classical SVMC plays a far less significant role, and results in a ground-state probability (after 10 000 sweeps) two orders of magnitude lower than a 100-ns AME evolved anneal.…”

Section: Dynamical Simulationssupporting

confidence: 70%

“…Improvements to groundstate probability can also be realized if we pause mid-anneal and allow the system to thermalize near the minimum gap [25][26][27]. However, to what extent thermalization is beneficial is still an active area of research, with lower noise quantum annealers (i.e., those with lower thermalization rates) being seen to improve tunneling ranges in local search (reverse) quantum anneals [28]. It was also shown in Ref.…”

Section: Introductionmentioning

confidence: 86%

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Perturbed ferromagnetic chain: Tunable test of hardness in the transverse-field Ising model

2022

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Quantum annealing in the transverse-field Ising model (TFIM) with open-system dynamics is known to use thermally assisted tunneling to drive computation. However, it is still subject to debate whether quantum systems in the presence of decoherence are more useful than those using classical dynamics to drive computation. We contribute to this debate by introducing the perturbed ferromagnetic chain (PFC), a chain of frustrated subsystems where the degree of frustration scales inversely with the perturbation introduced by a tunable parameter. This gives us an easily embeddable gadget whereby problem hardness can be tuned for systems of constant size. We outline the properties of the PFC and compare classical spin-vector Monte Carlo (SVMC) variants with the adiabatic quantum master equation. We demonstrate that SVMC methods get trapped in the exponentially large first-excited-state manifold when solving this frustrated problem, whereas evolution using quantum dynamics remains in the lowest energy eigenstates. This results in significant differences in ground-state probability when using either classical or quantum annealing dynamics in the TFIM.

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Section: Dynamical Simulationssupporting

confidence: 70%

Section: Introductionmentioning

confidence: 86%

Perturbed ferromagnetic chain: Tunable test of hardness in the transverse-field Ising model

2022

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“…Data from an experimental demonstration of using reverse annealing for local searching, first presented in Ref. [65], are shown in Fig. 3.…”

Section: Hybrid Forms Of Quantum Annealingmentioning

confidence: 99%

“…Data plot reproduced from Ref. [65]; cartoon illustration is original. The colors (shades of gray in print) and symbols in the cartoon reproduce those in the figure . The cross symbol indicates probability to be found in the false minimum, while the circles represent the probability to be found in the true minimum.…”

Section: Hybrid Forms Of Quantum Annealingmentioning

confidence: 99%

“…Chancellor [64] demonstrated how these techniques can be combined with other advanced controls to trade off between optimality and flexibility within solutions. Chancellor and Kendon [65] demonstrated that the underlying principle behind using reverse annealing for local search was correct and examined the effect of noise levels.…”

Section: Hybrid Forms Of Quantum Annealingmentioning

confidence: 99%

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Hybrid quantum-classical algorithms in the noisy intermediate-scale quantum era and beyond

Callison

Chancellor

2022

Phys. Rev. A

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Hybrid quantum-classical algorithms are central to much of the current research in quantum computing, particularly when considering the noisy intermediate-scale quantum (NISQ) era, with a number of experimental demonstrations having already been performed. In this perspective, we discuss in a very broad sense what it means for an algorithm to be hybrid quantum-classical. We first explore this concept very directly, by building a definition based on previous work in abstraction-representation theory, arguing that what makes an algorithm hybrid is not directly how it is run (or how many classical resources it consumes), but whether classical components are crucial to an underlying model of the computation. We then take a broader view of this question, reviewing a number of hybrid algorithms and discussing what makes them hybrid, as well as the history of how they emerged and considerations related to hardware. This leads into a natural discussion of what the future holds for these algorithms. To answer this question, we turn to the use of specialized processors in classical computing. The classical trend is not for new technology to completely replace the old, but to augment it. We argue that the evolution of quantum computing is unlikely to be different: Hybrid algorithms are likely here to stay well past the NISQ era and even into full fault tolerance, with the quantum processors augmenting the already powerful classical processors which exist by performing specialized tasks.

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Understanding domain-wall encoding theoretically and experimentally

Berwald

Chancellor

Dridi

2022

Phil. Trans. R. Soc. A.

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We analyse the method of encoding pairwise interactions of higher-than-binary discrete variables (these models are sometimes referred to as discrete quadratic models) into binary variables based on domain walls on one-dimensional Ising chains. We discuss how this is relevant to quantum annealing, but also many gate model algorithms such as VQE and QAOA. We theoretically show that for problems of practical interest for quantum computing and assuming only quadratic interactions are available between the binary variables, it is not possible to have a more efficient general encoding in terms of number of binary variables per discrete variable. We furthermore use a D-Wave Advantage 1.1 flux qubit quantum annealing computer to show that the dynamics effectively freeze later for a domain-wall encoding compared with a traditional one-hot encoding. This second result could help explain the dramatic performance improvement of domain wall over one-hot, which has been seen in a recent experiment on D-Wave hardware. This is an important result because usually problem encoding and the underlying physics are considered separately, our work suggests that considering them together may be a more useful paradigm. We argue that this experimental result is also likely to carry over to a number of other settings, we discuss how this has implications for gate-model and quantum-inspired algorithms. This article is part of the theme issue ‘Quantum annealing and computation: challenges and perspectives’.

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Experimental test of search range in quantum annealing

Cited by 9 publications

References 31 publications

Perturbed ferromagnetic chain: Tunable test of hardness in the transverse-field Ising model

Perturbed ferromagnetic chain: Tunable test of hardness in the transverse-field Ising model

Hybrid quantum-classical algorithms in the noisy intermediate-scale quantum era and beyond

Understanding domain-wall encoding theoretically and experimentally

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