Scalable Circuits for Preparing Ground States on Digital Quantum Computers: The Schwinger Model Vacuum on 100 Qubits

Journal Article · 17 April 2024 · PRX Quantum

DOI: https://doi.org/10.1103/prxquantum.5.020315 · OSTI ID:2338014

Farrell, Roland C.  ^[1]; Illa, Marc  ^[2]; Ciavarella, Anthony N.  ^[2]; Savage, Martin J.  ^[2]

---

1. University of Washington, Seattle, WA (United States); UW
2. University of Washington, Seattle, WA (United States)

The vacuum of the lattice Schwinger model is prepared on up to 100 qubits of IBM’s Eagle-processor quantum computers. A new algorithm to prepare the ground state of a gapped translationally invariant system on a quantum computer is presented, which we call “scalable circuits ADAPT-VQE” (SC-ADAPT-VQE). This algorithm uses the exponential decay of correlations between distant regions of the ground state, together with ADAPT-VQE, to construct quantum circuits for state preparation that can be scaled to arbitrarily large systems. These scalable circuits can be determined with use of classical computers, avoiding the challenging task of optimizing parameterized circuits on a quantum computer. SC-ADAPT-VQE is applied to the Schwinger model, and is shown to be systematically improvable, with an accuracy that converges exponentially with circuit depth. Both the structure of the circuits and the deviations of prepared wave functions are found to become independent of the number of spatial sites, L. This allows a controlled extrapolation of the circuits, determined with use of small or modest-sized systems, to arbitrarily large L. The circuits for the Schwinger model are determined on lattices up to L = 14 (28 qubits) with the Qiskit classical simulator, and are subsequently scaled up to prepare the L = 50 (100 qubits) vacuum on IBM’s 127-superconducting-qubit quantum computers ibm_brisbane and ibm_cusco. After introduction of an improved error-mitigation technique, which we call “operator decoherence renormalization”, the chiral condensate and charge-charge correlators obtained from the quantum computers are found to be in good agreement with classical matrix product state simulations.

• Research Organization: University of Washington, Seattle, WA (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Nuclear Physics (NP); USDOE Office of Science (SC), Basic Energy Sciences (BES). Scientific User Facilities (SUF)
• Grant/Contract Number: SC0020970; FG02-97ER41014; AC05-00OR22725
• OSTI ID: 2338014
• Alternate ID(s): OSTI ID: 2338202
• Report Number(s): IQuS@UW--21-060, NT@UW--23-13
• Journal Information: PRX Quantum, Journal Name: PRX Quantum Journal Issue: 2 Vol. 5; ISSN 2691-3399
• Publisher: American Physical Society (APS)Copyright Statement
• Country of Publication: United States
• Language: English