Cited by 172Quantum Mechanics and ApplicationsQuantum Computing Algorithms and ArchitectureQuantum Information and Cryptography

The DOI matches its Crossref record; 29 of the 29 references it cites were found in a registry or an index; none of the 10 sources its claims cite is checked for support yet.

Geometric derivation of the quantum speed limit

Open access
Jones, Philip J., Kok, Pieter·2010·Physical Review A

Abstract

The Mandelstam-Tamm and Margolus-Levitin inequalities play an important role in the study of quantum-mechanical processes in nature since they provide general limits on the speed of dynamical evolution. However, to date there has been only one derivation of the Margolus-Levitin inequality. In this paper, alternative geometric derivations for both inequalities are obtained from the statistical distance between quantum states. The inequalities are shown to hold for unitary evolution of pure and mixed states, and a counterexample to the inequalities is given for evolution described by completely positive trace-preserving maps. The counterexample shows that there is no quantum speed limit for nonunitary evolution.

Overview

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TL;DR

The paper gives alternative geometric derivations of the Mandelstam-Tamm and Margolus-Levitin quantum speed-limit inequalities from the statistical distance between quantum states. It shows these bounds hold for unitary evolution of pure and mixed states, and constructs a completely positive trace-preserving map counterexample that violates both, implying no general quantum speed limit for non-unitary evolution.

Key findings

  • Both inequalities are derived geometrically: Mandelstam-Tamm follows from the Fisher-information bound, while Margolus-Levitin follows from explicit differentiation of the Wootters distance and the Cauchy-Schwarz inequality.
  • The inequalities are shown to hold for unitary evolution of pure and mixed states; for mixed states, Margolus-Levitin is extended via purification, with the bound interpreted using the system’s average energy by choosing purifications made only of degenerate ground eigenstates.
  • A counterexample using a central qubit plus \(N\) satellite qubits, GHZ entanglement, phase shifts, and simultaneous CZ/Hadamard gates produces orthogonal initial and final states in time \(t < \pi\hbar/E_0\) when \(N\phi=\pi\), with \(E_\phi > E_0\) and \(g\) chosen appropriately; this violates both bounds and shows \(t\) can be made arbitrarily small by making \(E_\phi\) and \(g\) arbitrarily large.
  • The paper notes that mixed states can never attain either equality, and that states attaining the inequalities have the form of superpositions of energy eigenstates.

Methods

  • Theoretical derivation with no experimental data or sample; the work is a mathematical/geometric analysis of quantum speed limits.
  • Uses statistical distance for classical probability distributions and density matrices, Fisher information, Wootters distance, and Uhlmann purification to derive bounds on dynamical speed.
  • The non-unitary counterexample is analyzed with the stabilizer formalism for \(N+1\) qubits, including CZ, Hadamard, and phase-shift gates, and gate-time periodicity arguments.

Limitations

  • The paper states open questions: what general system-environment requirements allow violation of the speed limit; whether the strong interaction can be achieved noiselessly; whether noise may impose a practical speed limit; and whether general bounds can be based on environment properties rather than detailed dynamics.
  • The paper states the counterexample “may be very difficult to implement in practice” and that \(t\) can be made arbitrarily small by making \(E_\phi\) and \(g\) arbitrarily large.
  • Evident from the text: the counterexample is an idealized mathematical construction assuming simultaneous ideal gates and no noise; the mixed-state equality result is cited from prior work, and the derivation of the inequalities assumes unitary evolution.

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Integrity signals

Registry

Crossref · 10.1103/physreva.82.022107

Cites

29 of 29 references verified0 citation errors · 0 not checkable

Statistics

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Verification

Claims the paper makes

0 of 10 cited sources checked · 0 supported · 0 flagged

Show all 30 claims

  • It may state two separate claims as one. 5
  • The quote only partly states this claim. 1
  • Probably not a substantial claim. 4
8 of 8
  • The paper relies on this without support.

    To date there has been only one derivation of the Margolus-Levitin inequality.

    “However, to date there has been only one derivation of the Margolus-Levitin inequality.”
  • The paper relies on this without support.

    The purification is merely a mathematical construction, so unrestricted amounts of energy may be added to the system during the process and any extra energy added is physically meaningless.

    “At first glance this seems problematic since the purification is merely a mathematical construction and therefore unrestricted amounts of energy may be added to the system during the process.”
  • The paper relies on this without support.

    The Hadamard gate evolves a state halfway to an orthogonal state.

    “The Hadamard gate evolves a state halfway to an orthogonal state, and the speed limit for this gate can therefore be taken as half the time given in Eq. (45), with E 0 → Eq :”
3 of 3

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Citations

Cites

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Show all 29 references

Research works printed but not linked: 2

  1. L. Mandelstam, 1945, J. Phys. (USSR), 9, 249
  2. J. Uffink, 1994, Proceedings of the Third International Workshop on Squeezed States and Uncertainty Relations

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Items 101–172 of 172

Metadata

Authors
Jones, P. J., & Kok, P.
Affiliations
University of Sheffield (GB)
Venue
Physical Review A
Published
2010-08-16
Volume
82
Issue
2
ISSN
  • 0556-2791 (ISSN-L)
  • 1050-2947
  • 1094-1622
OpenAlex
W2008738328
Cited by
172
References
29
Citations by year
2026: 6 · 2025: 22 · 2024: 14 · 2023: 12 · 2022: 15 · 2021: 13 · 2020: 17 · 2019: 6 · 2018: 7 · 2017: 7 · 2016: 11 · 2015: 14 · 2014: 12 · 2013: 9 · 2012: 2
FWCI
2.74
Type
journal article
Language
en
Open access
Locations
  • Physical Review A (publishedVersion)
  • arXiv (Cornell University) (submittedVersion)
  • arXiv (Cornell University)
Topics
  • Physical Sciences › Physics and Astronomy › Atomic and Molecular Physics, and Optics › Quantum Mechanics and Applications
  • Physical Sciences › Computer Science › Artificial Intelligence › Quantum Computing Algorithms and Architecture
  • Physical Sciences › Physics and Astronomy › Atomic and Molecular Physics, and Optics › Quantum Information and Cryptography
Keywords
quantum speed limit, statistical distance, quantum states, unitary evolution, mixed states, completely positive trace-preserving maps, non-unitary evolution, counterexample

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