Cited by 2,329Quantum Computing Algorithms and ArchitectureQuantum many-body systemsQuantum Information and Cryptography

Barren plateaus in quantum neural network training landscapes

Open access
McClean, Jarrod R., Boixo, Sergio, Smelyanskiy, Vadim N., Babbush, Ryan, Neven, Hartmut·2018·Nature Communications

Abstract

Many experimental proposals for noisy intermediate scale quantum devices involve training a parameterized quantum circuit with a classical optimization loop. Such hybrid quantum-classical algorithms are popular for applications in quantum simulation, optimization, and machine learning. Due to its simplicity and hardware efficiency, random circuits are often proposed as initial guesses for exploring the space of quantum states. We show that the exponential dimension of Hilbert space and the gradient estimation complexity make this choice unsuitable for hybrid quantum-classical algorithms run on more than a few qubits. Specifically, we show that for a wide class of reasonable parameterized quantum circuits, the probability that the gradient along any reasonable direction is non-zero to some fixed precision is exponentially small as a function of the number of qubits. We argue that this is related to the 2-design characteristic of random circuits, and that solutions to this problem must be studied.

The claims and statistics of this paper haven’t been checked yet.

Run the check — free, no account needed. It reads the open-access text and checks the sources it cites.

A few free checks a day · papers already verified open instantly · results are public

Integrity signals

Registry

Crossref · 10.1038/s41467-018-07090-4

Cites

50 of 50 references verified0 citation errors · 0 not checkable

Statistics

Claims the paper makes

The claims and statistics of this paper haven’t been checked yet.

Run the check — free, no account needed. It reads the open-access text and checks the sources it cites.

A few free checks a day · papers already verified open instantly · results are public

Claims other papers make about this one

Each is checked against this paper’s own text: does it say what the citing paper says it does?

  • The expectation value of the gradient of the objective function corresponding to randomly initialized PQCs decays exponentially to zero as a function of the number of qubits.

    “It was recently shown that the expectation value of the gradient of the objective function corresponding to randomly initialized PQCs (RPQC) decays exponentially to zero as a function of the number of qubits (McClean et al. , 2018).”

    From Noisy intermediate-scale quantum algorithms (2022) · cites this paper as McClean et al., 2018

    The Methods state that, under the paper’s RPQC assumptions, the expected gradient is exactly zero; it is the variance that decays exponentially with the number of qubits. The Numerical simulations section reports exponential decay in the measured expected value and its spread, but that does not establish an exponentially decaying theoretical expectation. (LLM, conf=0.88)

    Experimental — accuracy not yet measured
  • These quantum machine learning approaches need careful consideration of subtle issues that do not appear in classical algorithms and are strongly intertwined with the underlying hardware.

    “Regardless of the conditions of their advantages, these approaches need careful consideration of subtle issues (see, e.g., Refs.[112-115]) that do not appear in classical algorithms and are, in particular, strongly intertwined with the underlying hardware.”
  • Variational-state quantum metrology variationally searches for the optimal probe state.

    “Variational-state quantum metrology variationally searches for the optimal probe state [190-193].”

    From Variational quantum algorithms (2021) · cites this paper as [192]

    The Introduction describes optimizing parameterized quantum circuits, but discusses applications in simulation, optimization, machine learning, and error correction—not metrology. Searches for variational-state quantum metrology and optimal probe states found no passage explaining whether that method searches for an optimal probe state. (LLM, conf=0.73)

    Experimental — accuracy not yet measured
  • Two of the new entangling blocks are designed to implement number-conserving operators, more suitable for simulations of molecular systems, and can be implemented natively on superconducting processors with transmon qubits.

    “Two of these new blocks are designed to implement number-conserving operators, more suitable for simulations of molecular systems, and can be implemented natively on superconducting processor with transmon qubits 340-342 .”

    From Quantum Chemistry in the Age of Quantum Computing (2019) · cites this paper as [341]

  • When training is carried out classically, it may become hard due to Barren plateaus, especially for large data sets.

    “However, the training phase, when carried out classically, may itself become hard due to the emergence of so-called Barren plateaus, especially for large data sets.[230,231]”

    From Quantum Computing for Molecular Biology** (2023) · cites this paper as [230]

Self-check

Percentages, sums and reported differences re-computed from the paper’s own numbers.

The self-check needs the paper’s full text.

Cites

Flagged first, then by citations

Research works printed but not linked: 1

  1. [23]Farhi,E. & Neven, H. Classification with quantum neural networks on near term processors. Preprint at https://arxiv.org/abs/1802.06002 (2018). · arXiv

Cited by

Sorted by citations

Authors
McClean, J. R., Boixo, S., Smelyanskiy, V. N., Babbush, R., & Neven, H.
Affiliations
Google (United States) (US)
Corresponding author
  • McClean, Jarrod R.
  • Boixo, Sergio
  • Smelyanskiy, Vadim N.
Venue
Nature Communications
Published
2018-11-16
Volume
9
Issue
1
Pages
4812-4812
ISSN
2041-1723 (ISSN-L)
OpenAlex
W2794444783
Cited by
2,329
References
50
Citations by year
2026: 551 · 2025: 494 · 2024: 365 · 2023: 330 · 2022: 256 · 2021: 218 · 2020: 76 · 2019: 35 · 2018: 4
FWCI
46.92
Type
journal article
Language
en
Open access
Locations
  • Nature Communications (publishedVersion, cc-by)
  • Europe PMC (PubMed Central) (publishedVersion, cc-by)
  • PubMed Central (publishedVersion, cc-by)
  • PubMed (publishedVersion)
  • arXiv (Cornell University) (submittedVersion)
  • RePEc: Research Papers in Economics (submittedVersion)
  • DOAJ (DOAJ: Directory of Open Access Journals) (submittedVersion, cc-by-sa)
  • DOAJ (DOAJ: Directory of Open Access Journals) (submittedVersion)
  • arXiv (Cornell University)
Topics
  • Physical Sciences › Computer Science › Artificial Intelligence › Quantum Computing Algorithms and Architecture
  • Physical Sciences › Physics and Astronomy › Atomic and Molecular Physics, and Optics › Quantum many-body systems
  • Physical Sciences › Computer Science › Artificial Intelligence › Quantum Information and Cryptography
Keywords
barren plateaus, quantum neural networks, hybrid quantum-classical algorithms, variational quantum circuits, random circuits, gradient estimation, noisy intermediate-scale quantum computing, quantum machine learning

About these checks

Registry, retraction, Cites and statistics results are computed, not judged, with one exception: a printed reference that no index lists is read once by a model before it counts as a citation error. Claims are extracted by a model and kept only when their quote appears verbatim in the text; each cited source is then checked, with a model’s help, for whether it says what the claim relies on. Those verdicts can be wrong — read the claim’s quote and the cited source before relying on one.

Statistics and arithmetic are recomputed, not judged.

Confidence bands are shown only for fields calibrated on our annotated test set. None is calibrated yet, so no band is shown.

What counts as a claim ›How we measure confidence ›How we check this ›

Are you an author, or do you see a problem with this page? Request a review