Experimental realization of classical Z 2 spin liquids in a programmable quantum device

Journal Article · 13 August 2021 · Physical Review. B

DOI: https://doi.org/10.1103/physrevb.104.l081107 · OSTI ID:1852997

Zhou, Shiyu  ^[1]; Green, Dmitry ^[2]; Dahl, Edward D. ^[3]; Chamon, Claudio ^[4]

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1. Boston Univ., MA (United States); OSTI
2. Boston Univ., MA (United States); Research PULSE, LLC, New York, NY (United States)
3. Cold Quanta, Inc., Boulder, CO (United States)
4. Boston Univ., MA (United States)

We build and probe a Z₂ spin liquid in a programmable quantum device, the D-Wave DW-2000Q. Specifically, we observe the classical eight-vertex and six-vertex (spin ice) states and transitions between them. To realize this state of matter, we design a Hamiltonian with combinatorial gauge symmetry using only pairwise-qubit interactions and a transverse field, i.e., interactions which are accessible in this quantum device. The combinatorial gauge symmetry remains exact along the full quantum annealing path, landing the system onto the classical eight-vertex model at the endpoint of the path. The output configurations from the device allow us to directly observe the loop structure of the classical model. Moreover, we deform the Hamiltonian so as to vary the weights of the eight vertices and show that we can selectively attain the classical six-vertex (ice) model, or drive the system into a ferromagnetic state. Additionally, we present studies of the classical phase diagram of the system as a function of the eight-vertex deformations and effective temperature, which we control by varying the relative strengths of the programmable couplings, and we show that the experimental results are consistent with theoretical analysis. Finally, we identify additional capabilities that, if added to these devices, would allow us to realize Z₂ quantum spin liquids on which to build topological qubits.

• Research Organization: Los Alamos National Laboratory (LANL), Los Alamos, NM (United States); Northeastern Univ., Boston, MA (United States)
• Sponsoring Organization: USDOE Office of Science (SC)
• Grant/Contract Number: SC0019275
• OSTI ID: 1852997
• Journal Information: Physical Review. B, Journal Name: Physical Review. B Journal Issue: 8 Vol. 104; ISSN 2469-9950
• Publisher: American Physical Society (APS)Copyright Statement
• Country of Publication: United States
• Language: English