Abstract
Josephson junctions are the basis for the most sensitive magnetic flux detectors, the definition of the unit volt by the Josephson voltage standard, and superconducting digital and quantum computing. They result from the coupling of two coherent quantum states, as they occur in superconductors, superfluids, atomic Bose Einstein Condensates (BECs), and exciton-polariton condensates. In their ground state, Josephson junctions are characterized by an intrinsic phase jump. Controlling this phase jump is fundamental for applications in computing. Here, we experimentally demonstrate controllable phase relations between photon BECs resulting from particle exchange in a thermo-optically tunable potential landscape. Our experiment realizes an optical analog of a controllable 0,π-Josephson junction. By connecting several junctions, we can study a reconfigurable 4-condensate system demonstrating the potential of our approach for analog spin-glass simulation. More generally, the combination of static and dynamic nanostructuring techniques introduced in our work offers a powerful platform for the implementation of adaptive optical systems for paraxial light in and outside of thermal equilibrium.1 MoreReceived 14 January 2021Revised 6 May 2021Accepted 10 May 2021DOI:https://doi.org/10.1103/PhysRevResearch.3.023167Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasBose gasesBose-Einstein condensatesPhysical SystemsOptical microcavitiesOrganic microcavitiesPolariton condensateAtomic, Molecular & Optical
Highlights
Finding the energetic ground state of a magnet with disordered couplings is a complicated combinatorial problem
For the XY model, the proposed physical platforms are based on superconducting qubits [9], lasers [10], atomic Bose-Einstein condensates (BECs) [11], and polariton condensates [12,13,14,15,16,17]
The high contrast of the observed stripe pattern indicates first-order coherences close to unity. The fact that this level of coherence is reached when integrating over one Gaussian pump pulse proves that the coupling in our junction is neither dependent on optical gain nor influenced by self-interactions
Summary
Finding the energetic ground state of a magnet with disordered couplings is a complicated combinatorial problem. It is known that many important optimization problems in machine learning, logistics, computer chip design, and DNA sequencing can be mathematically mapped to an equivalent spin-glass problem [1]. For the Ising model, a first generation of analog spin-glass simulators has been realized using networks of superconducting qubits [4,5] and optical parametric oscillators (OPOs) [6,7,8]. Whether these simulators already offer a computational advantage over the more conventional von Neumann computer architecture is currently a matter of controversy.
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