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 Z72: Simulating macrosopic quantum systems on NISQ devices |
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Sponsoring Units: DQI Chair: Mario Motta, IBM Research - Almaden Room: Room 406 |
Friday, March 10, 2023 11:30AM - 11:42AM |
Z72.00001: Quantum embedding approaches for materials simulations on quantum computers Francois Jamet, Abhishek Agarwal, Ivan Rungger Quantum embedding approaches for materials simulations, such as the dynamical mean-field theory (DMFT), provide corrections to first-principles calculations for strongly correlated electrons, which are poorly described at lower levels of theory. These embedding methods are computationally demanding on classical computing architectures and hence remain restricted to small systems, limiting the scope of their applicability. |
Friday, March 10, 2023 11:42AM - 11:54AM |
Z72.00002: Quantum computing simulation of nonlinear optical response in Hubbard models Peter P Orth, Anirban Mukherjee, Yong-Xin Yao, Alexander Huynh, Thais V Trevisan Multidimensional coherent spectroscopy (MDCS) has become a valuable tool to analyze electronic excitations in correlated quantum materials. By exposing a system to a sequence of weak coherent optical light pulses, the nonlinear response signals from different excitations can be separated in the two- (or higher) dimensional frequency space, disentangling properties that appear convoluted in the linear response regime. While it is straightforward to calculate the MDCS response in noninteracting systems, where one has full knowledge of the complete excitation spectrum, the lack thereof in interacting systems makes this a challenging problem. Here we show that the task is well-suited for noisy intermediate-scale quantum (NISQ) computers that can efficiently simulate the time evolution of the interacting wavefunction between the different light pulse. Focusing on the paradigmatic electronic Hubbard model, we benchmark the capabilities of current quantum hardware by computing the nonlinear electric response based on Trotter time evolution of the quantum state and discuss the physical insight that MDCS reveals. |
Friday, March 10, 2023 11:54AM - 12:06PM |
Z72.00003: Effective calculation of the Green's function in the time domain on near-term quantum processors Francesco Libbi, Jacopo Rizzo, Francesco Tacchino, Nicola Marzari, Ivano Tavernelli We propose an improved quantum algorithm to calculate the Green’s function through real-time propagation, |
Friday, March 10, 2023 12:06PM - 12:18PM |
Z72.00004: Modelling carbon capture on metal-organic frameworks with quantum computing Wassil Sennane, Marko J Rancic, Gabriel Greene-Diniz, David Zsolt Manrique, Yann Magnin, Philippe Cordier, Philip Llewellyn, Michal Krompiec, David Muñoz Ramo, Elvira Shishenina Despite the recent progress in quantum computational algorithms for chemistry, there is a dearth of quantum computational simulations focused on material science applications, especially for the energy sector, where next generation sorbing materials are urgently needed to battle climate change. To drive their development, quantum computing is applied to the problem of CO2 adsorption in Al-fumarate Metal-Organic Frameworks. Fragmentation strategies based on Density Matrix Embedding Theory are applied, using a variational quantum algorithm as a fragment solver, along with active space selection to minimise qubit number. By investigating different fragmentation strategies and solvers, we propose a methodology to apply quantum computing to Al-fumarate interacting with a CO2 molecule, demonstrating the feasibility of treating a complex porous system as a concrete application of quantum computing. Our work paves the way for the use of quantum computing techniques in the quest of sorbents optimisation for more efficient carbon capture and conversion applications. |
Friday, March 10, 2023 12:18PM - 12:30PM |
Z72.00005: Bounds on Trotter Depth for Quantum Simulation of Some Important Condensed Matter Models Ryan Scott, Nathan M Myers, Woo-Ram Lee, Kwon Park, Vito W Scarola Trotterization of quantum algorithms is typically regarded as a difficult problem in the context of quantum computing because the Trotterized algorithmic complexity is estimated to scale prohibitively with the number of particles in the system. Typical complexity estimates are given in several orders of magnitude even for a relatively small number of particles. Nevertheless, information can still be obtained regarding the difficulty by comparing the relative scaling of the Trotter depth. In this way, we can determine which models will be of greater or lesser utility as quantum technology advances and the algorithms themselves become tractable. We consider some representative models and algorithms and compare their relative complexity. We also present novel methods for calculating the Trotter error based on their physical considerations. We draw conclusions regarding which models are more or less tractable for near-term quantum devices. |
Friday, March 10, 2023 12:30PM - 12:42PM |
Z72.00006: Making Trotterization adaptive for NISQ devices and beyond Hongzheng Zhao, Roderich Moessner, Marin Bukov?, Markus Heyl The digital simulation of quantum many-body dynamics, one of the most promising applications of quantum computers, involves Trotterization as a key element. It is an outstanding challenge to formulate a quantum algorithm allowing for adaptive Trotter time steps. This is particularly relevant for today's noisy intermediate scale quantum devices, where the minimization of the circuit depth is a central optimization task. Here, we introduce an adaptive Trotterization scheme providing a controlled solution of the quantum many-body dynamics of local observables. Our quantum algorithm outperforms conventional fixed-time step Trotterization schemes in a quantum quench and even allows for a controlled asymptotic long-time error, where Trotterized dynamics generically enter challenging regimes. This adaptive method can also be generalized to protect various other kinds of symmetries, which we illustrate by preserving the local Gauss's law in a lattice gauge theory. We discuss the requirements imposed by experimental resources, and point out that our adaptive Trotterization scheme can be of use also in numerical approaches based on Trotterization such as in time-evolving block decimation methods. |
Friday, March 10, 2023 12:42PM - 12:54PM |
Z72.00007: Benchmarking quantum simulation costs for many-body models Nathan M Myers, Ryan Scott, Kwon Park, Vito W Scarola Quantum computers offer the potential to efficiently simulate the dynamics of quantum systems, a task whose difficulty scales exponentially with system size on classical devices. To assess the potential for near-term quantum computers to simulate many-body systems we compare two significant measures of computational cost, the maximum Pauli depth and a bound on the number of Trotter steps needed to accurately simulate the system's time evolution, for two prominent and closely related many-body models, the Hubbard and the t-J model. We find that, despite the t-J model possessing a substantially smaller Hilbert space than the Hubbard model, its maximum Pauli depth is significantly larger. Alternatively, the optimal choice of model for minimizing the number of Trotter steps depends heavily on the model parameters. |
Friday, March 10, 2023 12:54PM - 1:06PM Author not Attending |
Z72.00008: Short depth algorithm for high temperature Gibbs state sampling jeffrey cohn, Norhan M Eassa, Mahmoud Moustafa Sampling from Gibbs states on a quantum computer is a notoriously hard problem. Even problems that are classically tractable can require large |
Friday, March 10, 2023 1:06PM - 1:18PM |
Z72.00009: Quantum Computation of Phase Transition in φ4 Scalar Field Theory Shane Thompson, George Siopsis It has been demonstrated that the critical point of the phase transition in φ4 scalar quantum field theory in one space and time dimension can be approximated via a Gaussian Effective Potential (GEP). Here we demonstrate how this critical point may be estimated on quantum hardware. We perform quantum computations with various lattice sizes and show that there is evidence of a transition from a symmetric phase to a symmetry-broken phase. The two-site case is implemented on actual quantum hardware, while we show via simulations that the continuum critical point lies at λ/m2 ∼ 61.2, where λ is the coupling and m is the renormalized mass. To compute the effective potential we first use the Variational Quantum Eigensolver algorithm (VQE) to determine the parameters for the Gaussian states. We then use these parameters to compute the effective potential as a function of 〈φ〉, using varying levels of hybrid quantum-classical computation. By modifying the Ansatz state, one can extend this procedure beyond GEP’s in order to demonstrate the second-order nature of the true phase transition, as the GEP transition is only first-order. |
Friday, March 10, 2023 1:18PM - 1:30PM |
Z72.00010: Preparing quantum ensembles using mid-circuit measurements John Stenger, Stephen Hellberg, Daniel Gunlycke Preparing a quantum-statistical ensemble on a quantum computer has application in many fields including simulating equilibrium physics, solving optimization problems, and training Boltzman machines. However, non-trivial ensembles cannot be prepared using unitary quantum gates alone. Therefore, we propose to prepare quantum ensembles by taking advantage of another resource available in quantum computing, quantum measurements. I will discuss the intimate relationship between quantum measurements and the entropy of a quantum statistical ensemble. Using mid-circuit quantum measurements, we are able to control the entropy of the quantum statistical ensemble, thereby, opening up the possibility to calculate the Helmholtz free energy of a simulated system. |
Friday, March 10, 2023 1:30PM - 1:42PM |
Z72.00011: Variational Microcanonical Estimator Klee Pollock, Thomas Iadecola, Peter P Orth An important target for noisy intermediate-scale quantum computers is to calculate thermal properties of complex interacting quantum systems. We propose a variational quantum algorithm for estimating microcanonical expectation values in a nonintegrable model. Using a relaxed criterion for convergence of the variational optimization loop, the algorithm generates weakly entangled superpositions of eigenstates at a given target energy density. These states can in turn be used to estimate microcanonical averages of local operators via the eigenstate thermalization hypothesis (ETH) in combination with classical averaging over a sufficiently large ensemble of variational states. We apply the algorithm to the one-dimensional mixed field Ising model, where it converges for ansatz circuits of roughly linear depth in system size. This allows us to present results for up to 13 qubits. The most accurate thermal estimates are produced at intermediate energy density, the range usually considered to be the most difficult to capture. We also connect our problem to recent works investigating the underpinnings of the ETH, in particular the pseudo-random nature of off-diagonal matrix elements of local operators in highly excited energy eigenstates. |
Friday, March 10, 2023 1:42PM - 1:54PM |
Z72.00012: Extensions of the Linear Embedding Quantum Algorithm for Lattice Boltzmann Fluid Simulation Wael Itani, Katepalli R Sreenivasan We advance our prior work on a quantum algorithm for the lattice Boltzmann scheme of an incompressible, single-phase fluid. The work is based on the linearization approach due to Kowalski by noting the equivalence between classical orthogonal polynomials and bosonic operators in Hilbert space for describing the evolution of a nonlinear system. We compare embedding variables in a bosonic Fock space with those in a generic binary representation. We discuss the favorable aspects of the lattice Boltzmann formulation, as well as the issue of normalization, and present numerical results of the linearized matrix-embedding of the collision operator, acting on normalized and unnormalized state vectors. We introduce an approach to achieving non-unitary evolution, utilizing additional bosonic modes in the Fock space, benefitting from the nature of nonlinearity in the lattice Boltzmann equations, and present it as an alternative to the linear combination of unitaries that utilize additional ancilla qubits. We discuss the limitations of such an approach. |
Friday, March 10, 2023 1:54PM - 2:06PM Author not Attending |
Z72.00013: Simulating the non-Hermitian skin effect on a quantum computer Ruizhe Shen, Tianqi Chen, Bo Yang, Ching Hua Lee Non-Hermitian physics has gained considerable attention in the recent years, particularly for the non-Hermitian skin effect (NHSE). While the NHSE has been realized in various classical metamaterials and even ultracold atomic arrays, it has not been realized in full generality on a universal quantum processor. To realize the NHSE on a quantum computer, not only must the time evolution operator be non-unitary, it must also act over sufficiently many qubits to implement spatial non-reciprocity. In this talk, we describe how such non-unitary operations can be implemented by embedding them in a quantum circuit with ancilla qubits. We show how we use this approach to implement the paradigmatic non-Hermitian Su-Schrieffer-Heeger (nH-SSH) model on a noisy IBM quantum processor, with the main signature of the NHSE being asymmetric spatial propagation and attenuation. To minimize errors from inevitable noise, the evolution is performed in a trainable circuit using the variational quantum algorithm (VQA). Our study demonstrates a critical step forward in the quantum simulation of non-Hermitian lattices in present-day quantum computers and facilitates future research of non-Hermitian many-body physics. |
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