Bulletin of the American Physical Society
APS March Meeting 2023
Volume 68, Number 3
Las Vegas, Nevada (March 5-10)
Virtual (March 20-22); Time Zone: Pacific Time
Session LL08: V: Quantum Simulation |
Hide Abstracts |
Sponsoring Units: DQI Chair: Orkesh Nurbolat, Nanjing University Room: Virtual Room 8 |
Tuesday, March 21, 2023 5:00AM - 5:12AM |
LL08.00001: Fast-forwarding quantum simulation with real-time quantum Krylov subspace algorithms Cristian L Cortes, Stephen K Gray, Eugene DePrince, III Quantum subspace diagonalization (QSD) algorithms have emerged as a competitive family of algorithms that avoid many of the optimization pitfalls associated with parameterized quantum circuit algorithms. While the vast majority of the QSD algorithms have focused on solving the eigenpair problem for ground, excited-state, and thermal observable estimation, there has been a lot less work in considering QSD algorithms for the problem of quantum dynamical simulation. In this work, we propose several quantum Krylov fast-forwarding (QKFF) algorithms capable of predicting long-time dynamics well beyond the coherence time of current quantum hardware. Our algorithms use real-time evolved Krylov basis states prepared on the quantum computer and a multi-reference subspace method to ensure convergence towards high-fidelity, long-time dynamics. In particular, we show that the proposed multi-reference methodology provides a systematic way of trading off circuit depth with classical post-processing complexity. We also demonstrate the efficacy of our approach through numerical implementations for several quantum chemistry problems including the calculation of the auto-correlation and dipole moment correlation functions. |
Tuesday, March 21, 2023 5:12AM - 5:24AM |
LL08.00002: Simulating large-size quantum spin chains on cloud-based superconducting quantum computers Hongye Yu, Tzu-Chieh Wei, Yusheng Zhao Quantum computers have the potential to efficiently simulate large-scale quantum systems for which classical approaches are bound to fail. Even though several existing quantum devices now feature total qubit numbers of more than one hundred, their applicability remains plagued by the presence of noise and errors. Thus, the degree to which large quantum systems can successfully be simulated on these devices remains unclear. Here, we report on cloud simulations performed on several of IBM's superconducting quantum computers to simulate ground states of spin chains having a wide range of system sizes up to one hundred and two qubits. We find that the ground-state energies extracted from realizations across different quantum computers and system sizes reach the expected values to within errors that are small (i.e. on the percent level), including the inference of the energy density in the thermodynamic limit from these values. We achieve this accuracy through a combination of physics-motivated variational Ansatzes, and efficient, scalable energy-measurement and error-mitigation protocols, including the use of a reference state in the zero-noise extrapolation. By using a 102-qubit system, we have been able to successfully apply up to 3186 CNOT gates in a single circuit when performing gate-error mitigation. Our accurate, error-mitigated results for random parameters in the Ansatz states suggest that a standalone hybrid quantum-classical variational approach for large-scale XXZ models is feasible. |
Tuesday, March 21, 2023 5:24AM - 5:36AM |
LL08.00003: Variational Quantum Simulations of the Lindblad Equation on Near-Term Quantum Computers Tasneem M Watad, Netanel Lindner Studying the nonunitary dynamics of open quantum systems is of a paramount importance due to the inevitable presence of decoherence and dissipation in realistic strongly correlated systems. In this work, we introduce a variational hybrid quantum algorithm to simulate the Lindblad master equation for time-evolving Markovian open quantum systems on near-term quantum computers. We also illustrate how can it be implemented to solve the adjoint Lindblad equation for time-evolving quantum observables in the Heisenberg picture framework. We design and optimize low-depth variational quantum circuits that efficiently capture dynamics for open quantum systems, and highlight the difference between them and those used for capturing the dynamics of isolated quantum systems. We benchmark and test the algorithm on different system sizes, showing its potential and consistency with near-term hardware capabilities. |
Tuesday, March 21, 2023 5:36AM - 5:48AM |
LL08.00004: Simulation of open quantum system dynamics based on the generalized quantum master equation on quantum computing devices Yuchen Wang, Ellen Mulvihill, Zixuan Hu, Ningyi Lyu, Saurabh Shivpuje, Yudan Liu, Micheline B Soley, Eitan Geva, Victor S Batista, Sabre Kais The simulation of open quantum system dynamics, namely the reduced dynamics of a quantum system coupled to a quantum bath, is the cornerstone of quantum rate theory, optical response theory and decoherence science, which are central concepts in modern physics and chemistry. |
Tuesday, March 21, 2023 5:48AM - 6:00AM |
LL08.00005: Vibrational structure on quantum computers Marco Majland The simulation of quantum many-body physics is expected to provide early quantum advantages with applications in both academia and industry. One of the primary challenges prohibiting such demonstrations for near-term devices amount to excessive quantum resource requirements and measurement overheads for relevant physical quantities such as ground state energies. With major differences between electronic and vibrational structure of molecules, it is expected that the symmetries of vibrational Hamiltonians may be exploited to obtain quantum advantages prior to the electronic counterpart. Such symmetries are presented in this presentation with emphasis on choice of ansatz and runtime estimates. |
Tuesday, March 21, 2023 6:00AM - 6:12AM |
LL08.00006: Double-bracket flow quantum algorithm for diagonalization Marek Gluza A quantum algorithm for preparing eigenstates of quantum systems is presented which makes use of only forward and backward evolutions under a prescribed Hamiltonian and phase flips. It is based on the Glazek-Wilson-Wegner flow method from condensed-matter physics or more generally double-bracket flows considered in dynamical systems. The phase flips are used to implement a dephasing of off-diagonal interaction terms and evolution reversal is employed for the quantum computer to approximate the group commutator needed for unitary propagation under the double-bracket generator of the diagonalizing flow. The presented algorithm is recursive and involves no qubit overheads. Its efficacy for near-term quantum devices is discussed using numerical examples. In particular, variational double-bracket flow generators, optimized flow step durations and heuristics for pinching via efficient unitary mixing approximations are considered. More broadly, this work opens a pathway for constructing purposeful quantum algorithms based on double-bracket flows also for tasks different from diagonalization and thus enlarges the quantum computing toolkit geared towards practical physics problems. |
Tuesday, March 21, 2023 6:12AM - 6:24AM |
LL08.00007: Local Variational Quantum Compilation of Large-Scale Hamiltonian Dynamics Yuya O Nakagawa, Kaoru Mizuta, Kosuke Mitarai, Keisuke Fujii The implementation of time-evolution operators on quantum circuits is important for quantum simulation. However, the standard method, Trotterization, requires a huge number of gates to achieve desirable accuracy. Here, we propose a local variational quantum compilation (LVQC) algorithm, which allows us to accurately and efficiently compile time-evolution operators on a large-scale quantum system by optimization with smaller-size quantum systems. LVQC utilizes a subsystem cost function, which approximates the fidelity of the whole circuit, defined for each subsystem that is as large as the approximate causal cones generated by the Lieb-Robinson (LR) bound. We rigorously derive its scaling property with respect to the subsystem size and show that the optimization conducted on the subsystem size leads to the compilation of whole-system time-evolution operators. As a result, LVQC runs with limited-size quantum computers or classical simulators that can handle such smaller quantum systems. For instance, finite-ranged and short-ranged interacting L-size systems can be compiled with O(L0)- or O(logL)-size quantum systems depending on the observables of interest. Furthermore, since this formalism relies only on the LR bound, it can efficiently construct time-evolution operators of various systems in generic dimensions involving finite-, short-, and long-ranged interactions. We also numerically demonstrate the LVQC algorithm for one-dimensional systems. Through the employment of classical simulation by time-evolving block decimation, we succeed in compressing the depth of the time-evolution operators up to 40 qubits by the compilation for 20 qubits. LVQC not only provides classical protocols for designing large-scale quantum circuits but also sheds light on applications of intermediate-scale quantum devices in implementing algorithms in larger-scale quantum devices. |
Tuesday, March 21, 2023 6:24AM - 6:36AM |
LL08.00008: Approximate encoding of quantum states using shallow circuits Matan Ben Dov A common requirement of quantum simulations and algorithms is the preparation of complex states through sequences of 2-qubit gates. For a generic quantum state, the number of gates grows exponentially with the number of qubits, thereby setting a strict barrier for exact state preparation on near-term quantum devices. In this talk, I will present an efficient method for creating an approximate encoding of a target state using a limited number of gates [1]. In the first part of the talk, I will focus on a classical implementation of the algorithm and demonstrate its performance by comparing the optimal and suboptimal circuits on real devices. Then, in the second part of the talk, I will consider a direct implementation of the proposed algorithm on a quantum computer and show how to overcome inherent barren plateaus by employing a local cost function rather than a global one. I will further examine how many shots are required to reach optimization convergence and show that the number of shots scales merely polynomially with the number of qubits. [1] arXiv: https://arxiv.org/pdf/2207.00028.pdf |
Tuesday, March 21, 2023 6:36AM - 6:48AM |
LL08.00009: Simulation of an Exactly-Solvable Nuclear Model on NISQ Devices and Simulators Ken W Robbins Noisy Intermediate-Scale Quantum (NISQ) computers are promising tools but are not yet able to perform fault tolerant quantum simulations We use simulation of the exactly solvable Lipkin-Meshkov-Glick (LMG) model as a benchmarking tool for several NISQ devices, simulators and methods. We also discuss qualities of non-compact bosonic encodings that are not present in fermionic encodings such as the Jordan-Wigner, Parity or Bravyi-Kitaev. Simulation of the N-particle LMG Hamiltonian with the Variational Quantum Eigensolver (VQE) requires O(N) qubits and O(N) gates. Estimation of the LMG Hamiltonian expectation value requires O(1) distinct measurement bases for any number of particles. The classical resources required to prepare and solve the problem scale polynomially with N. Because both the classical and quantum resources required scale efficiently as a function of N, simulation of the LMG model is useful as a benchmarking tool even at large problem sizes. |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700