Bulletin of the American Physical Society
APS March Meeting 2021
Monday–Friday, March 15–19, 2021; Virtual; Time Zone: Central Daylight Time, USA
Session A34: Quantum Annealing and Optimization IFocus Live

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Sponsoring Units: DQI Chair: Zoe Gonzalez Izquierdo 
Monday, March 15, 2021 8:00AM  8:36AM Live 
A34.00001: Catalyst Hamiltonians in Quantum Adiabatic Optimization: How much can they help? Invited Speaker: Tameem Albash Increased experimental control of quantum annealing systems has lead to a resurgence of interest in exploring different interpolation paths for quantum adiabatic optimization. In this talk, we review recent work on interpolations with a `catalyst’ Hamiltonian, corresponding to interpolations with an intermediate Hamiltonian that is different from the driver and problem Hamiltonians. For special cases, both offdiagonal and diagonal (in the computational basis) catalysts can allow for dramatic performance enhancements by eliminating exponentially closing minimum gaps along the interpolation, but we caution that these known examples have simple energy landscapes, making them poor examples of computationally hard problems. There remains no clear understanding or recipe for when these new interpolations can give performance enhancements more generally. This highlights the need for dramatically new insights and methods but also more experimental capabilities to further explore these new approaches. 
Monday, March 15, 2021 8:36AM  8:48AM Live 
A34.00002: Coherent oscillations in diabatic quantum annealing schedules Robbyn Trappen, Xi Dai, Daniel Tennant, Denis Melanson, Ali Yurtalan, Rui Yang, Rabindra Das, David K Kim, Alexander Melville, Bethany Niedzielski, William Oliver, Jonilyn Yoder, Steven Weber, Andrew James Kerman, Joseph Gibson, Jeffrey Grover, Steven Dissler, James I Basham, Sergey Novikov, Tameem Albash, Evgeny Mozgunov, Mostafa Khezri, Huo Chen, Daniel Lidar, Adrian Lupascu Diabatic transitions in quantum annealing protocols provide a potential route to speedup over classical algorithms via bypassing adiabatic ground state evolution. Theoretical studies involving multiple diabatic transitions show oscillations in the ground state probability as a function of anneal time, highlighting the importance of coherence in quantum annealing. We discuss the path towards the experimental study of this effect, using single and multiple qubits and present some recent experimental results on capacitivelyshunted flux qubits which provide insight into the role of coherence and noise in smallgap settings. 
Monday, March 15, 2021 8:48AM  9:00AM Live 
A34.00003: Customized annealing schedules Mostafa Khezri, Evgeny Mozgunov, Daniel Lidar In a typical quantum annealing protocol, the system starts with a transverse field Hamiltonian which is gradually turned off and replaced by a longitudinal Hamiltonian. The ground state of this longitudinal Hamiltonian contains the solution to the Ising problem of interest that it encodes. The probability of finding the system in that ground state may depend on how we make the transition from the transverse field to the longitudinal Hamiltonian. Therefore having precise control over these annealing schedules can be a powerful tool for increasing success probabilities. 
Monday, March 15, 2021 9:00AM  9:12AM Live 
A34.00004: Fair Sampling and Entanglement in TransverseField Quantum Annealing Asher Lantz, Chris M Herdman While ground states of a classical Ising model spin glass can be found using transversefield quantum annealing, for instances with ground state degeneracy, quantum annealing is known not to always efficiently sample all ground states. After annealing, in certain instances all ground states are equally sampled (fair sampling); in other instances the probability of measuring some ground states is reduced. In this work we investigate the entanglement structure of ground states in a fullyconnected transverse field Ising spin glass. We use numerical diagonalization to quantify the bipartite entanglement via entanglement entropy during the annealing process. Given the absence of locality in the fullyconnected spin glass, we investigate the distribution of entanglement entropy over all equal size bipartitions. We identify signatures of the degeneracy, hamming distance between classical ground states, and fair sampling in the entanglement distribution for weak transverse fields. 
Monday, March 15, 2021 9:12AM  9:24AM Live 
A34.00005: The Perils of Embedding for Quantum Sampling Jeffrey Marshall, Gianni Mossi, Eleanor G Rieffel In Phys. Rev. Research 2, 023020 (2020) it was shown that minor embedding can be detrimental for classical thermal sampling. Here we generalize these results by considering quantum thermal sampling in the transversefield Ising model, i.e. sampling in the computational basis a Hamiltonian with nonzero off diagonal terms. In the quantum case, loosely speaking, it is even harder to preserve the correct distribution properties, due to the fact it is typically not possible to diagonalize the quantum Hamiltonian. 
Monday, March 15, 2021 9:24AM  9:36AM 
A34.00006: Experimental studies of reverse annealing of pspin problem on DWave quantum annealer Yuki Bando, Ka Wa Yip, Hidetoshi Nishimori, Daniel Lidar Iterated reverse annealing (IRA) is a formalism of reverse annealing implemented in current quantum annealers. The system is prepared in a trial solution state, annealed reversely to an inversion point, and then annealed forwardly. It may also be iterated with the last output state as new input. 
Monday, March 15, 2021 9:36AM  9:48AM Live 
A34.00007: Programmable Quantum Annealing Architectures with Ising Quantum Wires Xingze Qiu, Peter Zoller, Xiaopeng Li Quantum annealing is a computation protocol exploiting quantum advantage in solving searching and optimization problems. Regarding hardware implementation, atomic systems provide a controllable platform with unique scalability. However, the longrange interactions that generically appear in quantum annealing models meet extreme challenge for atomic systems to engineer and program. In this talk we will discuss the question of engineering longrange interactions by locallycoupled Ising ferromagnetic quantum wires [1]. We show that the alltoall coupled quantum annealer can be mapped to a completely local architecture on a regular 3D cubic lattice. This local architecture can then be realized in atomic systems, including atoms in optical lattices and Rydberg tweezer arrays. We demonstrate that this architecture can be used to solve difficult computation problems such as MaxCut and prime factorization. 
Monday, March 15, 2021 9:48AM  10:00AM Live 
A34.00008: Energy Efficient Mobile Network Routing using Hybrid Quantum Algorithm Jie Chen, Prasanna Date, Nicholas Chancellor, Atiquzzaman Mohammed, Hongjian Sun, Cormac Sreenan, Viv Kendon

Monday, March 15, 2021 10:00AM  10:12AM Live 
A34.00009: Spin representation of bifurcationbased quantum annealing with Kerr parametric oscillators Ryoji Miyazaki A scheme using parametrically driven oscillators with Kerr nonlinearity (Kerr parametric oscillators, KPOs) was proposed as a method of adiabatic quantum optimization, also called bifurcationbased quantum annealing. In this scheme a KPO with gradually increasing pump field generates the cat state, which is interpreted as superposition of up and down states of an Ising spin. In this process for interacting KPOs the interaction makes each KPO select one of the two coherent states, namely the up or down state, as the ground state at the final point of the process. The resulting state corresponds to a solution of combinatorial optimization problems. The correspondence to spin configurations is clarified at the final point, while possible spin representation is unclear in the middle of the process, where the solution is searched for by the system. We transform interacting KPOs to spin systems and discuss the scheme in terms of the spin representation. We also investigate the obtained spin systems and compare them to the original KPOs to evaluate the validity of our transformation. 
Monday, March 15, 2021 10:12AM  10:24AM Live 
A34.00010: Multispin chain gadget with exponentially small gap controlled by a single spin Xi Dai, Robbyn Trappen, Daniel M Tennant, Denis Melanson, Muhammet Ali Yurtalan, Rui Yang, Alexander Melville, Bethany Niedzielski, Rabindra Das, David K Kim, William Oliver, Jonilyn Yoder, Steven Weber, Andrew James Kerman, Joseph Gibson, Jeffrey Grover, Steven M Disseler, James I Basham, Sergey Novikov, Evgeny Mozgunov, Mostafa Khezri, Huo Chen, Daniel Lidar, Tameem Albash, Adrian Lupascu We propose an annealing protocol with a multispin chain gadget where the minimum spectral gap closes exponentially with system size and can be controlled by acting only on one spin. This gadget can be realized on a chain of capacitivelyshunted flux qubits. By performing LandauZenerStuckelberg interferometry, we can learn more about the noise in the system. By performing a LandauZener sweep with a locally adiabatic schedule, the adiabatic timescale is quadratically improved over a linear schedule. We discuss experimental results and implications for quantum annealers with advanced control capabilities. 
Monday, March 15, 2021 10:24AM  10:36AM Live 
A34.00011: Reinforcement learning assisted quantum adiabatic algorithm design Jian Lin, Zhengfeng Zhang, Junping Zhang, Xiaopeng Li We develop a framework to optimize the adiabatic quantum algorithm for prime factorization using a quadratic Ising Hamiltonian encoding. In comparing the quantum adiabatic algorithm with the classical simulated annealing methods, we find rare problem instances which are difficult to solve for both classical and quantum annealing. We then adopt deep reinforcement learning directly targeting the rare difficult problem instances. By machine learning against rare problem instances, the overall performance of the quantum adiabatic algorithm is substantially improved. This provides a novel approach for quantum algorithm design with reinforcement learning. 
Monday, March 15, 2021 10:36AM  10:48AM Live 
A34.00012: Adiabatic reverse annealing with dephasing Gianluca Passarelli, Ka Wa Yip, Daniel Lidar, Procolo Lucignano Adiabatic Reverse Annealing (ARA) is a variant of quantum annealing (QA) exploiting path modification to perform a local search in the solution space of optimization problems. Starting from a classical configuration supposedly close to the target solution, in ARA quantum fluctuations are nonmonotonically varied so as to improve the quality of the trial solution. Compared to Iterated Reverse Annealing (IRA), ARA can exponentially speed up QA by avoiding firstorder quantum critical points in the phase diagram of the optimization problem. 
Monday, March 15, 2021 10:48AM  11:00AM On Demand 
A34.00013: An energetic perspective on rapid quenches in quantum annealing Adam Callison, Max Festenstein, Jie Chen, Laurentiu Nita, Viv Kendon, Nicholas Chancellor Welldeveloped theoretical tools exist to analyse how quantum dynamics can solve computational problems by varying Hamiltonians slowly (adiabatically). However, relatively few tools exist for the opposite limit of rapid quenches, used in quantum annealing and quantum walks. We develop a theoretical understanding and several practical tools for this regime. By analysing various energy expectation values, we show that monotonic quenches will yield a better result on average than random guessing. By characterising local dynamics, we identify cases where rapid quenches will lead to a substantially improved numerical scaling. We then use these tools to develop heuristics for choosing control parameters. 
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