---
_id: '11471'
abstract:
- lang: eng
  text: 'Variational quantum algorithms are promising algorithms for achieving quantum
    advantage on nearterm devices. The quantum hardware is used to implement a variational
    wave function and measure observables, whereas the classical computer is used
    to store and update the variational parameters. The optimization landscape of
    expressive variational ansätze is however dominated by large regions in parameter
    space, known as barren plateaus, with vanishing gradients, which prevents efficient
    optimization. In this work we propose a general algorithm to avoid barren plateaus
    in the initialization and throughout the optimization. To this end we define a
    notion of weak barren plateaus (WBPs) based on the entropies of local reduced
    density matrices. The presence of WBPs can be efficiently quantified using recently
    introduced shadow tomography of the quantum state with a classical computer. We
    demonstrate that avoidance of WBPs suffices to ensure sizable gradients in the
    initialization. In addition, we demonstrate that decreasing the gradient step
    size, guided by the entropies allows WBPs to be avoided during the optimization
    process. This paves the way for efficient barren plateau-free optimization on
    near-term devices. '
acknowledgement: "We thank Marco Cerezo, Zoe Holmes, and Nicholas Hunter-Jones for
  fruitful discussion and valuable feedback. We also acknowledge Adam Smith, Johannes
  Jakob Meyer, and Victor V. Albert for comments on the paper. The simulations were
  performed in the Julia programming\r\nlanguage [65] using the Yao module [66]. S.H.S.,
  R.A.M., A.A.M. and M.S. acknowledge support by the European Research Council (ERC)
  under the European Union’s Horizon 2020 research and innovation program (Grant Agreement
  No. 850899)."
article_number: '020365'
article_processing_charge: No
article_type: original
arxiv: 1
author:
- first_name: Stefan
  full_name: Sack, Stefan
  id: dd622248-f6e0-11ea-865d-ce382a1c81a5
  last_name: Sack
  orcid: 0000-0001-5400-8508
- first_name: Raimel A
  full_name: Medina Ramos, Raimel A
  id: CE680B90-D85A-11E9-B684-C920E6697425
  last_name: Medina Ramos
  orcid: 0000-0002-5383-2869
- first_name: Alexios
  full_name: Michailidis, Alexios
  id: 36EBAD38-F248-11E8-B48F-1D18A9856A87
  last_name: Michailidis
  orcid: 0000-0002-8443-1064
- first_name: Richard
  full_name: Kueng, Richard
  last_name: Kueng
- first_name: Maksym
  full_name: Serbyn, Maksym
  id: 47809E7E-F248-11E8-B48F-1D18A9856A87
  last_name: Serbyn
  orcid: 0000-0002-2399-5827
citation:
  ama: Sack S, Medina Ramos RA, Michailidis A, Kueng R, Serbyn M. Avoiding barren
    plateaus using classical shadows. <i>PRX Quantum</i>. 2022;3(2). doi:<a href="https://doi.org/10.1103/prxquantum.3.020365">10.1103/prxquantum.3.020365</a>
  apa: Sack, S., Medina Ramos, R. A., Michailidis, A., Kueng, R., &#38; Serbyn, M.
    (2022). Avoiding barren plateaus using classical shadows. <i>PRX Quantum</i>.
    American Physical Society. <a href="https://doi.org/10.1103/prxquantum.3.020365">https://doi.org/10.1103/prxquantum.3.020365</a>
  chicago: Sack, Stefan, Raimel A Medina Ramos, Alexios Michailidis, Richard Kueng,
    and Maksym Serbyn. “Avoiding Barren Plateaus Using Classical Shadows.” <i>PRX
    Quantum</i>. American Physical Society, 2022. <a href="https://doi.org/10.1103/prxquantum.3.020365">https://doi.org/10.1103/prxquantum.3.020365</a>.
  ieee: S. Sack, R. A. Medina Ramos, A. Michailidis, R. Kueng, and M. Serbyn, “Avoiding
    barren plateaus using classical shadows,” <i>PRX Quantum</i>, vol. 3, no. 2. American
    Physical Society, 2022.
  ista: Sack S, Medina Ramos RA, Michailidis A, Kueng R, Serbyn M. 2022. Avoiding
    barren plateaus using classical shadows. PRX Quantum. 3(2), 020365.
  mla: Sack, Stefan, et al. “Avoiding Barren Plateaus Using Classical Shadows.” <i>PRX
    Quantum</i>, vol. 3, no. 2, 020365, American Physical Society, 2022, doi:<a href="https://doi.org/10.1103/prxquantum.3.020365">10.1103/prxquantum.3.020365</a>.
  short: S. Sack, R.A. Medina Ramos, A. Michailidis, R. Kueng, M. Serbyn, PRX Quantum
    3 (2022).
date_created: 2022-06-29T20:21:32Z
date_published: 2022-06-29T00:00:00Z
date_updated: 2023-12-13T14:47:24Z
day: '29'
ddc:
- '530'
department:
- _id: MaSe
doi: 10.1103/prxquantum.3.020365
ec_funded: 1
external_id:
  arxiv:
  - '2201.08194'
  isi:
  - '000822564300001'
file:
- access_level: open_access
  checksum: a7706b28d24a0e32a55ea04b82a2df43
  content_type: application/pdf
  creator: dernst
  date_created: 2022-06-30T07:14:48Z
  date_updated: 2022-06-30T07:14:48Z
  file_id: '11472'
  file_name: 2022_PRXQuantum_Sack.pdf
  file_size: 4231591
  relation: main_file
  success: 1
file_date_updated: 2022-06-30T07:14:48Z
has_accepted_license: '1'
intvolume: '         3'
isi: 1
issue: '2'
keyword:
- General Medicine
language:
- iso: eng
month: '06'
oa: 1
oa_version: Published Version
project:
- _id: 23841C26-32DE-11EA-91FC-C7463DDC885E
  call_identifier: H2020
  grant_number: '850899'
  name: 'Non-Ergodic Quantum Matter: Universality, Dynamics and Control'
publication: PRX Quantum
publication_identifier:
  issn:
  - 2691-3399
publication_status: published
publisher: American Physical Society
quality_controlled: '1'
related_material:
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    relation: dissertation_contains
    status: public
status: public
title: Avoiding barren plateaus using classical shadows
tmp:
  image: /images/cc_by.png
  legal_code_url: https://creativecommons.org/licenses/by/4.0/legalcode
  name: Creative Commons Attribution 4.0 International Public License (CC-BY 4.0)
  short: CC BY (4.0)
type: journal_article
user_id: 4359f0d1-fa6c-11eb-b949-802e58b17ae8
volume: 3
year: '2022'
...
---
_id: '9114'
abstract:
- lang: eng
  text: "Microwave photonics lends the advantages of fiber optics to electronic sensing
    and communication systems. In contrast to nonlinear optics, electro-optic devices
    so far require classical modulation fields whose variance is dominated by electronic
    or thermal noise rather than quantum fluctuations. Here we demonstrate bidirectional
    single-sideband conversion of X band microwave to C band telecom light with a
    microwave mode occupancy as low as 0.025 ± 0.005 and an added output noise of
    less than or equal to 0.074 photons. This is facilitated by radiative cooling
    and a triply resonant ultra-low-loss transducer operating at millikelvin temperatures.
    The high bandwidth of 10.7 MHz and total (internal) photon conversion\r\nefficiency
    of 0.03% (0.67%) combined with the extremely slow heating rate of 1.1 added output
    noise photons per second for the highest available pump power of 1.48 mW puts
    near-unity efficiency pulsed quantum transduction within reach. Together with
    the non-Gaussian resources of superconducting qubits this might provide the practical
    foundation to extend the range and scope of current quantum networks in analogy
    to electrical repeaters in classical fiber optic communication."
acknowledged_ssus:
- _id: M-Shop
acknowledgement: "The authors acknowledge the support of T. Menner, A. Arslani, and
  T. Asenov from the Miba machine shop for machining the microwave cavity, and thank
  S. Barzanjeh, F. Sedlmeir, and C. Marquardt for fruitful discussions. This work
  is supported by IST Austria and the European Research Council under Grant No. 758053
  (ERC StG QUNNECT). W.H. is the recipient of an ISTplus postdoctoral fellowship with
  funding from the European Union’s Horizon 2020 research and innovation program under
  the Marie Skłodowska-Curie Grant No. 754411.\r\nG.A. is the recipient of a DOC fellowship
  of the Austrian Academy of Sciences at IST Austria. J.M.F. acknowledges support
  from the Austrian Science Fund (FWF) through BeyondC (F71) and the European Union’s
  Horizon 2020 research and innovation program under Grant No. 899354 (FET Open SuperQuLAN).
  H.G.L.S. acknowledges support from the Aotearoa/New Zealand’s MBIE Endeavour Smart
  Ideas Grant No UOOX1805."
article_number: '020315'
article_processing_charge: No
article_type: original
author:
- first_name: William J
  full_name: Hease, William J
  id: 29705398-F248-11E8-B48F-1D18A9856A87
  last_name: Hease
  orcid: 0000-0001-9868-2166
- first_name: Alfredo R
  full_name: Rueda Sanchez, Alfredo R
  id: 3B82B0F8-F248-11E8-B48F-1D18A9856A87
  last_name: Rueda Sanchez
  orcid: 0000-0001-6249-5860
- first_name: Rishabh
  full_name: Sahu, Rishabh
  id: 47D26E34-F248-11E8-B48F-1D18A9856A87
  last_name: Sahu
  orcid: 0000-0001-6264-2162
- first_name: Matthias
  full_name: Wulf, Matthias
  id: 45598606-F248-11E8-B48F-1D18A9856A87
  last_name: Wulf
  orcid: 0000-0001-6613-1378
- first_name: Georg M
  full_name: Arnold, Georg M
  id: 3770C838-F248-11E8-B48F-1D18A9856A87
  last_name: Arnold
  orcid: 0000-0003-1397-7876
- first_name: Harald G.L.
  full_name: Schwefel, Harald G.L.
  last_name: Schwefel
- first_name: Johannes M
  full_name: Fink, Johannes M
  id: 4B591CBA-F248-11E8-B48F-1D18A9856A87
  last_name: Fink
  orcid: 0000-0001-8112-028X
citation:
  ama: Hease WJ, Rueda Sanchez AR, Sahu R, et al. Bidirectional electro-optic wavelength
    conversion in the quantum ground state. <i>PRX Quantum</i>. 2020;1(2). doi:<a
    href="https://doi.org/10.1103/prxquantum.1.020315">10.1103/prxquantum.1.020315</a>
  apa: Hease, W. J., Rueda Sanchez, A. R., Sahu, R., Wulf, M., Arnold, G. M., Schwefel,
    H. G. L., &#38; Fink, J. M. (2020). Bidirectional electro-optic wavelength conversion
    in the quantum ground state. <i>PRX Quantum</i>. American Physical Society. <a
    href="https://doi.org/10.1103/prxquantum.1.020315">https://doi.org/10.1103/prxquantum.1.020315</a>
  chicago: Hease, William J, Alfredo R Rueda Sanchez, Rishabh Sahu, Matthias Wulf,
    Georg M Arnold, Harald G.L. Schwefel, and Johannes M Fink. “Bidirectional Electro-Optic
    Wavelength Conversion in the Quantum Ground State.” <i>PRX Quantum</i>. American
    Physical Society, 2020. <a href="https://doi.org/10.1103/prxquantum.1.020315">https://doi.org/10.1103/prxquantum.1.020315</a>.
  ieee: W. J. Hease <i>et al.</i>, “Bidirectional electro-optic wavelength conversion
    in the quantum ground state,” <i>PRX Quantum</i>, vol. 1, no. 2. American Physical
    Society, 2020.
  ista: Hease WJ, Rueda Sanchez AR, Sahu R, Wulf M, Arnold GM, Schwefel HGL, Fink
    JM. 2020. Bidirectional electro-optic wavelength conversion in the quantum ground
    state. PRX Quantum. 1(2), 020315.
  mla: Hease, William J., et al. “Bidirectional Electro-Optic Wavelength Conversion
    in the Quantum Ground State.” <i>PRX Quantum</i>, vol. 1, no. 2, 020315, American
    Physical Society, 2020, doi:<a href="https://doi.org/10.1103/prxquantum.1.020315">10.1103/prxquantum.1.020315</a>.
  short: W.J. Hease, A.R. Rueda Sanchez, R. Sahu, M. Wulf, G.M. Arnold, H.G.L. Schwefel,
    J.M. Fink, PRX Quantum 1 (2020).
date_created: 2021-02-12T10:41:28Z
date_published: 2020-11-23T00:00:00Z
date_updated: 2024-10-29T09:11:05Z
day: '23'
ddc:
- '530'
department:
- _id: JoFi
doi: 10.1103/prxquantum.1.020315
ec_funded: 1
external_id:
  isi:
  - '000674680100001'
file:
- access_level: open_access
  checksum: b70b12ded6d7660d4c9037eb09bfed0c
  content_type: application/pdf
  creator: dernst
  date_created: 2021-02-12T11:16:16Z
  date_updated: 2021-02-12T11:16:16Z
  file_id: '9115'
  file_name: 2020_PRXQuantum_Hease.pdf
  file_size: 2146924
  relation: main_file
  success: 1
file_date_updated: 2021-02-12T11:16:16Z
has_accepted_license: '1'
intvolume: '         1'
isi: 1
issue: '2'
language:
- iso: eng
month: '11'
oa: 1
oa_version: Published Version
project:
- _id: 26336814-B435-11E9-9278-68D0E5697425
  call_identifier: H2020
  grant_number: '758053'
  name: A Fiber Optic Transceiver for Superconducting Qubits
- _id: 260C2330-B435-11E9-9278-68D0E5697425
  call_identifier: H2020
  grant_number: '754411'
  name: ISTplus - Postdoctoral Fellowships
- _id: 9B868D20-BA93-11EA-9121-9846C619BF3A
  call_identifier: H2020
  grant_number: '899354'
  name: Quantum Local Area Networks with Superconducting Qubits
- _id: 26927A52-B435-11E9-9278-68D0E5697425
  call_identifier: FWF
  grant_number: F07105
  name: Integrating superconducting quantum circuits
- _id: 2671EB66-B435-11E9-9278-68D0E5697425
  name: Coherent on-chip conversion of superconducting qubit signals from microwaves
    to optical frequencies
publication: PRX Quantum
publication_identifier:
  issn:
  - 2691-3399
publication_status: published
publisher: American Physical Society
quality_controlled: '1'
related_material:
  link:
  - description: News on IST Homepage
    relation: press_release
    url: https://ist.ac.at/en/news/how-to-transport-microwave-quantum-information-via-optical-fiber/
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  - id: '13175'
    relation: dissertation_contains
    status: public
status: public
title: Bidirectional electro-optic wavelength conversion in the quantum ground state
tmp:
  image: /images/cc_by.png
  legal_code_url: https://creativecommons.org/licenses/by/4.0/legalcode
  name: Creative Commons Attribution 4.0 International Public License (CC-BY 4.0)
  short: CC BY (4.0)
type: journal_article
user_id: 4359f0d1-fa6c-11eb-b949-802e58b17ae8
volume: 1
year: '2020'
...