1. Key Laboratory of Atomic and Subatomic Structure and Quantum Control (Ministry of Education), Guangdong Basic Research Center of Excellence for Structure and Fundamental Interactions of Matter, and School of Physics, South China Normal University, Guangzhou 510006, China 2. Guangdong Provincial Key Laboratory of Quantum Engineering and Quantum Materials, Guangdong−Hong Kong Joint Laboratory of Quantum Matter, and Frontier Research Institute for Physics, South China Normal University, Guangzhou 510006, China
Solving non-Hermitian quantum many-body systems on a quantum computer by minimizing the variational energy is challenging as the energy can be complex. Here, we propose a variational quantum algorithm for solving the non-Hermitian Hamiltonian by minimizing a type of energy variance, where zero variance can naturally determine the eigenvalues and the associated left and right eigenstates. Moreover, the energy is set as a parameter in the cost function and can be tuned to scan the whole spectrum efficiently by using a two-step optimization scheme. Through numerical simulations, we demonstrate the algorithm for preparing the left and right eigenstates, verifying the biorthogonal relations, as well as evaluating the observables. We also investigate the impact of quantum noise on our algorithm and show that its performance can be largely improved using error mitigation techniques. Therefore, our work suggests an avenue for solving non-Hermitian quantum many-body systems with variational quantum algorithms on near-term noisy quantum computers.
Guo A. , J. Salamo G. , Duchesne D. , Morandotti R. , Volatier-Ravat M. , Aimez V. , A. Siviloglou G. , N. Christodoulides D. . Observation of PT-symmetry breaking in complex optical potentials. Phys. Rev. Lett., 2009, 103(9): 093902 https://doi.org/10.1103/PhysRevLett.103.093902
Dorey P. , Dunning C. , Tateo R. , equivalences Spectral . Bethe ansatz equations, and reality properties in PT-symmetric quantum mechanics. J. Phys. Math. Gen., 2001, 34(28): 5679 https://doi.org/10.1088/0305-4470/34/28/305
5
K. Özdemir Ş. , Rotter S. , Nori F. , Yang L. . Parity‒time symmetry and exceptional points in photonics. Nat. Mater., 2019, 18: 783 https://doi.org/10.1038/s41563-019-0304-9
Wang Z. , J. Lang L. , He L. . Emergent Mott insulators and non-Hermitian conservation laws in an interacting bosonic chain with noninteger filling and nonreciprocal hopping. Phys. Rev. B, 2022, 105(5): 054315 https://doi.org/10.1103/PhysRevB.105.054315
8
Jiang H. , J. Lang L. , Yang C. , L. Zhu S. , Chen S. . Interplay of non-Hermitian skin effects and Anderson localization in nonreciprocal quasiperiodic lattices. Phys. Rev. B, 2019, 100(5): 054301 https://doi.org/10.1103/PhysRevB.100.054301
9
J. Lang L. , Cai X. , Chen S. . Edge states and topological phases in one-dimensional optical superlattices. Phys. Rev. Lett., 2012, 108(22): 220401 https://doi.org/10.1103/PhysRevLett.108.220401
10
W. Zhang D. , Z. Tang L. , J. Lang L. , Yan H. , L. Zhu S. . Non-Hermitian topological Anderson insulators. Sci. China Phys. Mech. Astron., 2020, 63(6): 267062 https://doi.org/10.1007/s11433-020-1521-9
11
Z. Tang L. , Q. Zhang G. , F. Zhang L. , W. Zhang D. . Localization and topological transitions in non-Hermitian quasiperiodic lattices. Phys. Rev. A, 2021, 103(3): 033325 https://doi.org/10.1103/PhysRevA.103.033325
12
Z. Tang L. , F. Zhang L. , Q. Zhang G. , W. Zhang D. . Topological Anderson insulators in two-dimensional non-Hermitian disordered systems. Phys. Rev. A, 2020, 101(6): 063612 https://doi.org/10.1103/PhysRevA.101.063612
Song F. , Yao S. , Wang Z. . Non-Hermitian skin effect and chiral damping in open quantum systems. Phys. Rev. Lett., 2019, 123(17): 170401 https://doi.org/10.1103/PhysRevLett.123.170401
del Campo A. , L. Egusquiza I. , B. Plenio M. , F. Huelga S. . Quantum speed limits in open system dynamics. Phys. Rev. Lett., 2013, 110(5): 050403 https://doi.org/10.1103/PhysRevLett.110.050403
Chen G. , Song F. , L. Lado J. . Topological spin excitations in non-Hermitian spin chains with a generalized kernel polynomial algorithm. Phys. Rev. Lett., 2023, 130(10): 100401 https://doi.org/10.1103/PhysRevLett.130.100401
19
Jaschke D. , Montangero S. , D. Carr L. . One-dimensional many-body entangled open quantum systems with tensor network methods. Quantum Sci. Technol., 2018, 4(1): 013001 https://doi.org/10.1088/2058-9565/aae724
20
T. Fishman M. , Vanderstraeten L. , Zauner-Stauber V. , Haegeman J. , Verstraete F. . Faster methods for contracting infinite two-dimensional tensor networks. Phys. Rev. B, 2018, 98(23): 235148 https://doi.org/10.1103/PhysRevB.98.235148
21
Orús R. . A practical introduction to tensor networks: Matrix product states and projected entangled pair states. Ann. Phys., 2014, 349: 117 https://doi.org/10.1016/j.aop.2014.06.013
22
Wiesner S., Simulations of many-body quantum systems by a quantum computer, arXiv: quant-ph/9603028 (1996)
23
Poulin D. , Wocjan P. . Preparing ground states of quantum many-body systems on a quantum computer. Phys. Rev. Lett., 2009, 102(13): 130503 https://doi.org/10.1103/PhysRevLett.102.130503
24
S. Abrams D. , Lloyd S. . Simulation of many-body Fermi systems on a universal quantum computer. Phys. Rev. Lett., 1997, 79(13): 2586 https://doi.org/10.1103/PhysRevLett.79.2586
25
Smith A. , Kim M. , Pollmann F. , Knolle J. . Simulating quantum many-body dynamics on a current digital quantum computer. npj Quantum Inf., 2019, 5: 106 https://doi.org/10.1038/s41534-019-0217-0
26
Peruzzo A. , McClean J. , Shadbolt P. , H. Yung M. , Q. Zhou X. , J. Love P. , Aspuru-Guzik A. , L. O’brien J. . A variational eigenvalue solver on a photonic quantum processor. Nat. Commun., 2014, 5(1): 4213 https://doi.org/10.1038/ncomms5213
27
Kandala A. , Mezzacapo A. , Temme K. , Takita M. , Brink M. , M. Chow J. , M. Gambetta J. . Hardware-efficient variational quantum eigensolver for small molecules and quantum magnets. Nature, 2017, 549(7671): 242 https://doi.org/10.1038/nature23879
28
Tilly J. , Chen H. , Cao S. , Picozzi D. , Setia K. , Li Y. , Grant E. , Wossnig L. , Rungger I. , H. Booth G. , Tennyson J. . The variational quantum eigensolver: A review of methods and best practices. Phys. Rep., 2022, 986: 1 https://doi.org/10.1016/j.physrep.2022.08.003
29
A. Fedorov D. , Peng B. , Govind N. , Alexeev Y. . VQE method: A short survey and recent developments. Mater. Theory, 2022, 6(1): 2 https://doi.org/10.1186/s41313-021-00032-6
30
J. O’Malley P. , Babbush R. , D. Kivlichan I. , Romero J. , R. McClean J. , Barends R. , Kelly J. , Roushan P. , Tranter A. , Ding N. , Campbell B. , Chen Y. , Chen Z. , Chiaro B. , Dunsworth A. , G. Fowler A. , Jeffrey E. , Lucero E. , Megrant A. , Y. Mutus J. , Neeley M. , Neill C. , Quintana C. , Sank D. , Vainsencher A. , Wenner J. , C. White T. , V. Coveney P. , J. Love P. , Neven H. , Aspuru-Guzik A. , M. Martinis J. . Scalable quantum simulation of molecular energies. Phys. Rev. X, 2016, 6(3): 031007 https://doi.org/10.1103/PhysRevX.6.031007
31
L. Bosse J. , Montanaro A. . Probing ground-state properties of the kagome antiferromagnetic Heisenberg model using the variational quantum eigensolver. Phys. Rev. B, 2022, 105(9): 094409 https://doi.org/10.1103/PhysRevB.105.094409
32
Kattemölle J. , van Wezel J. . Variational quantum eigensolver for the Heisenberg antiferromagnet on the kagome lattice. Phys. Rev. B, 2022, 106(21): 214429 https://doi.org/10.1103/PhysRevB.106.214429
33
M. Nakanishi K. , Mitarai K. , Fujii K. . Subspace-search variational quantum eigensolver for excited states. Phys. Rev. Res., 2019, 1(3): 033062 https://doi.org/10.1103/PhysRevResearch.1.033062
Liu S. , X. Zhang S. , Y. Hsieh C. , Zhang S. , Yao H. . Probing many-body localization by excited-state variational quantum eigensolver. Phys. Rev. B, 2023, 107(2): 024204 https://doi.org/10.1103/PhysRevB.107.024204
36
X. Xie Q. , Liu S. , Zhao Y. . Orthogonal state reduction variational eigensolver for the excited-state calculations on quantum computers. J. Chem. Theory Comput., 2022, 18(6): 3737 https://doi.org/10.1021/acs.jctc.2c00159
37
B. Zhang D. , L. Chen B. , H. Yuan Z. , Yin T. . Variational quantum eigensolvers by variance minimization. Chin. Phys. B, 2022, 31(12): 120301 https://doi.org/10.1088/1674-1056/ac8a8d
38
L. Chen B. , B. Zhang D. . Variational quantum eigensolver with mutual variance-Hamiltonian optimization. Chin. Phys. Lett., 2023, 40(1): 010303 https://doi.org/10.1088/0256-307X/40/1/010303
39
Guo Z.T. Xu Z.Li M.You L.Yang S., Variational matrix product state approach for non-Hermitian system based on a companion Hermitian Hamiltonian, arXiv: 2210.14858 (2022)
40
Moiseyev N., Non-Hermitian Quantum Mechanics, Cambridge: Cambridge University Press, 2011
41
Banach S., Theory of Linear Operations, Elsevier, 1987
42
Cerezo M. , Arrasmith A. , Babbush R. , C. Benjamin S. , Endo S. , Fujii K. , R. McClean J. , Mitarai K. , Yuan X. , Cincio L. , J. Coles P. . Variational quantum algorithms. Nat. Rev. Phys., 2021, 3(9): 625 https://doi.org/10.1038/s42254-021-00348-9
43
Cleve R. , Ekert A. , Macchiavello C. , Mosca M. . Quantum algorithms revisited. Proc. Royal Soc. A, 1998, 454(1969): 339 https://doi.org/10.1098/rspa.1998.0164
Efthymiou S. , Ramos-Calderer S. , Bravo-Prieto C. , Pérez-Salinas A. , García-Martín D. , Garcia-Saez A. , I. Latorre J. , Carrazza S. . Qibo: A framework for quantum simulation with hardware acceleration. Quantum Sci. Technol., 2022, 7(1): 015018 https://doi.org/10.1088/2058-9565/ac39f5
46
R. Johansson J. , D. Nation P. , Nori F. . QuTiP: An open-source Python framework for the dynamics of open quantum systems. Comput. Phys. Commun., 2012, 183(8): 1760 https://doi.org/10.1016/j.cpc.2012.02.021
47
Gehlen G. . Critical and off-critical conformal analysis of the Ising quantum chain in an imaginary field. J. Phys. Math. Gen., 1991, 24(22): 5371 https://doi.org/10.1088/0305-4470/24/22/021
48
B. Sousa P.V. Ramos R., Universal quantum circuit for n-qubit quantum gate: A programmable quantum gate, arXiv: quant-ph/0602174 (2006)
49
D. Xie X. , Guo X. , Xing H. , Y. Xue Z. , B. Zhang D. , L. Zhu S. . Variational thermal quantum simulation of the lattice Schwinger model. Phys. Rev. D, 2022, 106(5): 054509 https://doi.org/10.1103/PhysRevD.106.054509
F. Richardson L. , A. Gaunt J. . VIII. The deferred approach to the limit. Philos. Trans. Royal Soc. Ser. A, 1927, 226(636‒646): 299 https://doi.org/10.1098/rsta.1927.0008