• Open Access

Quantum Virtual Cooling

Jordan Cotler, Soonwon Choi, Alexander Lukin, Hrant Gharibyan, Tarun Grover, M. Eric Tai, Matthew Rispoli, Robert Schittko, Philipp M. Preiss, Adam M. Kaufman, Markus Greiner, Hannes Pichler, and Patrick Hayden
Phys. Rev. X 9, 031013 – Published 29 July 2019

Abstract

We propose a quantum-information-based scheme to reduce the temperature of quantum many-body systems and access regimes beyond the current capability of conventional cooling techniques. We show that collective measurements on multiple copies of a system at finite temperature can simulate measurements of the same system at a lower temperature. This idea is illustrated for the example of ultracold atoms in optical lattices, where controlled tunnel coupling and quantum gas microscopy can be naturally combined to realize the required collective measurements to access a lower, virtual temperature. Our protocol is experimentally implemented for a Bose-Hubbard model on up to 12 sites, and we successfully extract expectation values of observables at half the temperature of the physical system. Additionally, we present related techniques that enable the extraction of zero-temperature states directly.

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  • Received 8 January 2019
  • Revised 25 May 2019

DOI:https://doi.org/10.1103/PhysRevX.9.031013

Published 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 Society

Physics Subject Headings (PhySH)

Quantum Information, Science & TechnologyAtomic, Molecular & OpticalInterdisciplinary Physics

Authors & Affiliations

Jordan Cotler1,*, Soonwon Choi2, Alexander Lukin3, Hrant Gharibyan1, Tarun Grover4, M. Eric Tai3, Matthew Rispoli3, Robert Schittko3, Philipp M. Preiss3,5, Adam M. Kaufman3,6, Markus Greiner3, Hannes Pichler7,3, and Patrick Hayden1

  • 1Stanford Institute for Theoretical Physics, Stanford University, Stanford, California 94305, USA
  • 2Department of Physics, University of California, Berkeley, California 94720, USA
  • 3Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
  • 4Department of Physics, University of California at San Diego, La Jolla, California 92093, USA
  • 5Physics Institute, Heidelberg University, 69120 Heidelberg, Germany
  • 6JILA, National Institute of Standards and Technology and University of Colorado, and Department of Physics, University of Colorado, Boulder, Colorado 80309, USA
  • 7ITAMP, Harvard-Smithsonian Center for Astrophysics, Cambridge, Massachusetts 02138, USA

  • *jcotler@stanford.edu

Popular Summary

Many quantum systems composed of interacting particles have exotic properties at very low temperatures. Techniques for cooling quantum systems have been a focal point of technological innovation in experimental physics for many years, expanding the frontier of the quantum realm. Is it possible to cool quantum systems to ever lower temperatures using the tools of quantum information? We find a surprising solution: Given two identical quantum systems, each at the same fixed temperature, we can use quantum information processing to measure information about a single system at half of that temperature.

We develop “quantum virtual cooling” and bring it to life experimentally in the lab. Our quantum system is composed of rubidium atoms confined by lasers to a thin tube, so that each atom can move only left or right. We take two such tubes and prepare identical quantum states at the same temperature. We then allow atoms to quantum tunnel between the two tubes in a controlled manner. By examining both systems, post-tunneling, under a quantum microscope, we can read out properties of a single tube at half of the temperature. Our experimental results match theoretical predictions: We can “virtually” probe a system at half of its physical temperature.

Going forward, we would like to use our technique to virtually cool a quantum system below a finite temperature phase transition and explore fermionic systems. We would also like to implement more experimentally sophisticated versions of our protocol.

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Vol. 9, Iss. 3 — July - September 2019

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