Bulletin of the American Physical Society
APS March Meeting 2020
Volume 65, Number 1
Monday–Friday, March 2–6, 2020; Denver, Colorado
Session J08: NISQ: Quantum Chemistry and Quantum Simulation II 
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Sponsoring Units: DQI Chair: Abhinav Kandala, IBM TJ Watson Research Center Room: 104 
Tuesday, March 3, 2020 2:30PM  2:42PM 
J08.00001: Simulating quantum systems on quantum computers Sean A Fischer, C Stephen Hellberg, Marco LanzagortaSaldana, Daniel Gunlycke In this presentation, we discuss a new mapping method—called symmetry configuration mapping (SCM)—that uses the symmetry of the physical system to isolate different parts of the computational space. As well as providing robustness against state leakage, this new approach allows the computation to be separated into a set of smaller independent calculations involving fewer quantum logic gate operations and fewer qubits. For a fluorine molecule, the numbers of quantum logic gate operations and qubits are reduced by factors of 3 and 4, respectively. These reductions have allowed us to solve for the full manybody ground state on the IBM Q “Poughkeepsie” quantum computer. As long as quantum computing resources remain limited, similar targetcustomized mappings are expected to be employed in quantum computing across all areas of application. 
Tuesday, March 3, 2020 2:42PM  2:54PM 
J08.00002: Studying manybody localization on a universal quantum computer Sonika Johri, Daiwei Zhu, Nhung Nguyen, Cinthia Alderete, kevin landsman, Norbert M Linke, Christopher Roy Monroe, Anne Matsuura An interacting disordered system may exhibit localized or thermal behavior depending on the ratio of the disorder to interaction strength. The study of this phenomena has been proposed as an application of nearterm quantum computers. However, it is known that most diagnostics of localization such as manybody level statistics and the failure of the eigenstate thermalization hypothesis do not survive coupling to a bath. One robust diagnostic theoretically known to survive introduction of noise are the spectral functions of local operators [1]. Signatures of localization in this diagnostic include a discrete spectrum and a gap at low frequencies. Here, we design an algorithm to compute the spectrum on a universal quantum computer using Trotterized timeevolution. Further, we implement the technique on a threequbit trapped ion system and find that we can clearly discern the vanishing of the lowfrequency response as the disorder increases. Thus, we show that for nearterm quantum computers, spectral functions of local operators provide a robust and scalable diagnostic for distinguishing between localized and thermal phases. 
Tuesday, March 3, 2020 2:54PM  3:06PM 
J08.00003: Towards material design applications in a quantum computer Panagiotis Barkoutsos, Fotios Gkritsis, Igor Sokolov, Pauline Jeanne Ollitrault, Stefan Woerner, Ivano Tavernelli Developing new materials for specific applications is an active field of research for both material science and quantum chemistry communities. The number of atomic compositions of molecular structures scales combinatorically with the size of the molecules, limiting the efficiency of classical algorithms. On the other hand, quantum computers can provide an efficient solution to the sampling of the chemical compound space. In this talk we propose a quantum algorithm with favorable scaling in resource requirements, allowing for the solution of the material design problem in currently available noisy quantum processors. The proposed scheme divides the problem into a classical optimization and a quantum search problem within a hybrid quantum classical algorithm. We demonstrate both in simulations (with and without noise) and in IBMQ quantum hardware the efficiency of our scheme and highlight the results in a few test cases. These preliminary results can serve as a basis for the development of further material design quantum algorithms for near term quantum computers. 
Tuesday, March 3, 2020 3:06PM  3:18PM 
J08.00004: Simulating quantum field theory in the lightfront formulation Michael Kreshchuk, William Kirby, Gary R Goldstein, PierreHugues Beauchemin, Peter Love We explore the possibility of simulating relativistic field theories in the lightfront (LF) formulation and argue that such a framework has numerous advantages as compared to both lattice and secondquantized equaltime approaches. These include a small number of physical degrees of freedom leading to reduced resource requirements, efficient encoding with modelindependent asymptotics, and sparse Hamiltonians. Many quantities of physical interest are naturally defined in the LF, resulting in simple measurements. 
Tuesday, March 3, 2020 3:18PM  3:30PM 
J08.00005: Simulating Dynamic Material Properties on NearTerm Quantum Computers Lindsay Bassman, Kuang Liu, Yifan Geng, Daniel Shebib, Aravind Krishnamoorthy, Shogo Fukushima, Fuyuki Shimojo, Rajiv Kalia, Aiichiro Nakano, Priya Vashishta Dynamic simulation of controllable electronic properties of materials offers insight into how to harness such tunability for use in myriad technologies. Recent successes have been achieved in computing static properties of small molecules on currently available quantum computers, however, simulating dynamical properties still remains a challenge. In this work, we demonstrate successful simulation of timedependent magnetization in a simplified model of an atomicallythin twodimensional material on IBM’s Q16 Melbourne quantum processor and Rigetti’s Aspen quantum processor. Near overlap between experimental results from the quantum computer and those theoretically derived from simulated noisy qubits indicates there is a good understanding of the largest sources of error currently faced on available quantum computers. This early proofofconcept gives hope that nearfuture quantum computers, capable of simulating larger systems, may soon be able to give insights into the dynamic control of tunable electronic properties in material. 
Tuesday, March 3, 2020 3:30PM  3:42PM 
J08.00006: Robust Preparation of Manybody Ground States in JaynesCummings Lattices Kang Cai, Prabin Parajuli, Chee Wei Wong, Guilu Long, Lin Tian Stronglycorrelated polaritons in JaynesCummings (JC) lattices can exhibit novel quantum phase transitions at integer fillings. However, it is often challenging to prepare such states with high fidelity, especially near the quantum critical points with a vanishing energy gap. Here we study the robust preparation of the manybody ground states of polaritons in a finitesized JC lattice by combining the techniques of quantum state engineering and adiabatic evolution. In the deep Mottinsulating or deep superfluid regimes, the manybody ground states can be generated with high fidelity by applying quantumengineered pulse sequences to the JC lattice. Using these states as the initial state and tuning the system parameters adiabatically, the manybody ground states in the intermediate regime can be reached. Our numerical result shows that the fidelity of the generated states can be significantly improved by employing a nonlinear ramping scheme during the adiabatic evolution. We derive the optimal nonlinear index analytically, which agrees well with the numerical result. This study gives insights into the preparation of manybody states in artificial quantum systems, such as quantum simulators. 
Tuesday, March 3, 2020 3:42PM  3:54PM 
J08.00007: Quantum Algorithm for Simulating a Driven Dissipative 3site Hubbard Ring Brian Rost, Lorenzo Del Re, Michael C Johnson, Alexander F Kemper, James Freericks Much research has been done concerning the simulation of closed quantum systems on near term quantum computers. Considerably less focus has been given to the simulation of open quantum systems, despite their importance as realistic models of real world systems. We consider the simulation of a three site Hubbard model driven by an electric field, connected to a Fermionic bath. This is the simplest model capable of stabilizing a nonzero steady state current with the added benefit that the fermionic bath admits an analytic solution in the noninteracting limit. We simulate this model classically using a master equation approach and provide an implementation for simulating it on a quantum computer. Even this simple model shows rich steady state behavior and offers a promising approach for simulating a variety of time dependent, driven, dissipative, open quantum systems. 
Tuesday, March 3, 2020 3:54PM  4:06PM 
J08.00008: Mapping Hamiltonians from material science onto nearterm quantum devices Norm Tubman, Bryan O'Gorman, Hitesh Changlani

Tuesday, March 3, 2020 4:06PM  4:18PM 
J08.00009: Determining Hamiltonian eigenstates on a quantum computer using quantum imaginary time evolution Mario Motta, Chong Sun, Adrian Tan, Matthew J O'Rourke, Erika Ye, Austin Minnich, Fernando Brandão, Garnet Chan The accurate computation of Hamiltonian ground and excited states on quantum computers stands to impact many problems in the physical and computer sciences, from quantum simulation to machine learning. Given the challenges posed in constructing largescale quantum computers, these tasks should be carried out in a resourceefficient way. We recently introduced [1] the quantum imaginary time evolution and quantum Lanczos algorithms, which are analogues of classical algorithms for finding ground and excited states. Compared with their classical counterparts, they require exponentially less space and time per iteration, and can be implemented without deep circuits and ancillae, or highdimensional optimizations. We discuss applications to spins and fermions. 
Tuesday, March 3, 2020 4:18PM  4:30PM 
J08.00010: Quantum Computation of the Ground and Excited State Energies Using Quantum Imaginary Time Evolution and Quantum Lanczos Methods Kubra Yeter Aydeniz, Raphael Pooser, George Siopsis Various methods have been developed for quantum computation of the ground and excited states of physical systems, but many of them require either large numbers of ancilla or high dimensional optimization. The quantum imaginary time evolution (QITE) and quantum Lanczos (QLanczos) methods proposed in [1] eschew the aforementioned issues. In this study, we demonstrate the application of these algorithms on a nontrivial quantum computation, using the deuteron binding energy as an example. With the correct choice of initial and final states we showed that the number of time steps in QITE and QLanczos can be reduced significantly, which commensurately simplifies the required quantum circuit and improves compatibility with NISQ devices. We performed these calculations on cloudaccessible IBMQ quantum computers, and with the application of readout error mitigation and Richardson error extrapolation, we obtained ground and approximate excited state energies within 3% of the theory. These results show promise for using the algorithms in future field theory, scattering, and chemistry calculations. 
Tuesday, March 3, 2020 4:30PM  4:42PM 
J08.00011: Drivendissipative quantum mechanics on a lattice: Describing a fermionic reservoir with the master equation Lorenzo Del Re, Brian Rost, Alexander F Kemper, James Freericks The possibility of simulating dissipative processes with digital circuits and quantum simulators, and using dissipation as a resource for state preparation, have created a renewed interest on the drivendissipative many body problem. 
Tuesday, March 3, 2020 4:42PM  4:54PM 
J08.00012: Quantum synchronization on the IBM Q system Martin Koppenhoefer, Christoph Bruder, Alexandre Roulet We report the first experimental demonstration of quantum synchronization. This is achieved by performing a digital simulation of a spin1 limitcycle oscillator on the quantum processors of the IBM Q system. Applying an external signal to the oscillator, we verify typical features of quantum synchronization and demonstrate an interferencebased quantum synchronization blockade. Our results show that stateoftheart noisy intermediatescale quantum processors are powerful enough to implement realistic open quantum systems. Finally, we discuss limitations of current quantum hardware and define requirements necessary to investigate more complex problems. 
Tuesday, March 3, 2020 4:54PM  5:06PM 
J08.00013: Quantum Digital Cooling Stefano Polla, Yaroslav Herasymenko, Thomas O'Brien We introduce a new method for digital preparation of ground states of a simulated Hamiltonians, inspired by cooling in nature and adapted to leverage the capabilities of digital quantum hardware. The cold bath is simulated by a single ancillary qubit, which is reset periodically and coupled to the system nonperturbatively. Studying this cooling method on a 1qubit system toy model allows us to optimize two cooling protocols based on weakcoupling and strongcoupling approaches. Extending these, we develop two scalable protocols for larger systems. 
Tuesday, March 3, 2020 5:06PM  5:18PM 
J08.00014: ResourceEfficient Quantum Algorithm for Protein Folding Ivano Tavernelli, Anton Robert, Panagiotis Barkoutsos, Stefan Woerner Due to the central role of proteins’ 3D structures in chemistry, biology and medicine applications (e.g., in drug discovery), protein folding has been intensively studied for over half a century. Although classical algorithms provide practical solutions for the conformation space sampling of small proteins, they cannot tackle the intrinsic NPhard complexity of the problem, even reduced to its simplest HydrophobicPolar model. 
Tuesday, March 3, 2020 5:18PM  5:30PM 
J08.00015: Digital quantum simulation of quantum vibrational dynamics and control Alicia Magann, Matthew D Grace, Herschel A Rabitz, Mohan Sarovar Quantum computers are expected to offer speedups for solving certain scientific problems. One example is digital quantum simulation, where sequences of quantum gates can be used to simulate the dynamics of quantum systems in polynomial time. This could have applications in simulations of quantum optimal control, which aim to identify shaped fields to drive a quantum system towards a designated control objective. In this talk, I will explore how digital quantum simulation could be used to make quantum optimal control simulations more tractable. I will introduce a framework that utilizes a quantum computer to simulate the fieldinduced dynamics of a quantum system in combination with classical optimization to update the field. As a demonstration of this framework, a quantum vibrational control problem will be considered. 
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