• Open Access

Theory of Quantum Super Impulses

Christopher Jarzynski
PRX Quantum 5, 010322 – Published 8 February 2024

Abstract

A quantum impulse is a brief but strong perturbation that produces a sudden change in a wave function ψ(x). We develop a theory of quantum impulses, distinguishing between ordinary and super impulses. An ordinary impulse paints a phase onto ψ, while a super impulse—the main focus of this paper—deforms the wave function under an invertible map, μ:xx. Borrowing tools from optimal-mass-transport theory and shortcuts to adiabaticity, we show how to design a super impulse that deforms a wave function under a desired map μ and we illustrate our results using solvable examples. We point out a strong connection between quantum and classical super impulses, expressed in terms of the path-integral formulation of quantum mechanics. We briefly discuss hybrid impulses, in which ordinary and super impulses are applied simultaneously. While our central results are derived for evolution under the time-dependent Schrödinger equation, they apply equally well to the time-dependent Gross-Pitaevskii equation and thus may be relevant for the manipulation of Bose-Einstein condensates.

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  • Received 4 August 2023
  • Accepted 10 January 2024

DOI:https://doi.org/10.1103/PRXQuantum.5.010322

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 & Technology

Authors & Affiliations

Christopher Jarzynski1,2,3,*

  • 1Department of Chemistry and Biochemistry, University of Maryland, College Park, Maryland 20742, USA
  • 2Institute for Physical Science and Technology, University of Maryland, College Park, Maryland 20742, USA
  • 3Department of Physics, University of Maryland, College Park, Maryland 20742, USA

  • *cjarzyns@umd.edu

Popular Summary

A well-aimed baseball bat hits its target, causing a sudden change in the direction of the ball’s motion. In introductory physics we refer to the explosive force that the bat exerts on the ball, acting over the brief interval during which bat and ball are in contact, as an impulse. We examine how analogous impulses affect quantum systems. We distinguish between two different flavors of impulses, ordinary and super, which differ in how the impulse’s strength scales with its duration. Super impulses—the main focus of our work—are stronger than ordinary ones.

Under appropriate conditions, a quantum super impulse suddenly deforms a system’s wave function: It translates, stretches, and squeezes various portions of the wave function in a generally nonlinear manner. Mathematically, this deformation is specified by a map of the system’s configuration space onto itself. As our main result, we pose and answer the following question: If we wish to deform a given initial wave function ψi under a map μ of our choice, how do we design a super impulse that achieves this goal?

While our paper is self-contained, it draws on theoretical tools from the fields of shortcuts to adiabaticity and optimal transport. To build intuition, we illustrate our results with simple examples for which the super impulse can be obtained analytically. Our results extend to many-body systems, in a mean-field approximation, and potentially open the way to the development of experimental tools for manipulating quantum systems.

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Vol. 5, Iss. 1 — February - April 2024

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It is not necessary to obtain permission to reuse this article or its components as it is available under the terms of the Creative Commons Attribution 4.0 International license. This license permits unrestricted use, distribution, and reproduction in any medium, provided attribution to the author(s) and the published article's title, journal citation, and DOI are maintained. Please note that some figures may have been included with permission from other third parties. It is your responsibility to obtain the proper permission from the rights holder directly for these figures.

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