I am a theoretical physicist at Princeton University. My interests are in many-body quantum mechanics and the interface between quantum and classical simulation. Here there are connections to be made between statistical mechanics, quantum information, and conventional condensed matter physics.

Recently, a set of problems that I have been focusing on concern the effects that measurements have on many-body quantum systems. These effects are practically relevant to quantum error correction, and to our understanding of the complexity of simulating quantum systems on classical computers. You can find a detailed explanation in this talk (from Simons Center, Berkeley), and an  even more detailed explanation in this talk (from Cornell). Our most recent work on this can be found on arXiv. There, using Google's superconducting quantum processors, we showed that measurement-induced collective phenomena can be detected in 'snapshots' of quantum states.

This summer (2025) I gave a lecture series at Berkeley as part of the NSF Challenge Institute for Quantum Computation (CIQC). There was also a livestream. The course covers the basics of quantum computation, starting from the perspective of quantum dynamics. The target audience is early graduate students in physics and chemistry, and only assumes a familiarity with basic quantum mechanics. Here are the notes.

Preprints

• https://arxiv.org/abs/2510.02275
  Lower bounds on the complexity of preparing mixed states
  Max McGinley, Samuel J Garratt

• https://arxiv.org/abs/2509.08890
  Machine learning the effects of many quantum measurements
  Wanda Hou, Samuel J. Garratt, Norhan M. Eassa, Eliott Rosenberg, Pedram Roushan, Yi-Zhuang You, Ehud Altman

• https://arxiv.org/abs/2504.12385

Learning transitions in classical Ising models and deformed toric codes
Malte Pütz, Samuel J. Garratt, Hidetoshi Nishimori, Simon Trebst, Guo-Yi Zhu

• https://arxiv.org/abs/2502.13218
  Entanglement and private information in many-body thermal states
  Samuel J. Garratt, Max McGinley

• https://arxiv.org/abs/2501.09084
  Goldstone mode of the broken helix in U(1) magnet EuIn2As2
  Alex Liebman-Pelaez, Samuel J. Garratt, Veronika Sunko, Yue Sun, Jian R. Soh,  Dharmalingam Prabhakaran, Andrew T. Boothroyd, Joseph Orenstein

• https://arxiv.org/abs/2410.13844

Post-measurement quantum Monte Carlo
Kriti Baweja, David J. Luitz, Samuel J. Garratt

• https://arxiv.org/abs/2407.07893
  Quantum Algorithm to Prepare Quasi-Stationary States
  Samuel J. Garratt, Soonwon Choi

Publications 

• Phys. Rev. B 112, 054436 (2025)

https://arxiv.org/abs/2502.09612
Superspin renormalization and slow relaxation in random spin systems
Yi J. Zhao, Samuel J. Garratt, Joel Moore

• Phys. Rev. B 111, 094316 (2025)
  https://arxiv.org/abs/2312.14234
  Operator dynamics in Floquet many-body systems
  Takato Yoshimura, Samuel J. Garratt, J. T. Chalker

• Phys. Rev. X Quantum 5, 030311 (2024)

https://arxiv.org/abs/2305.20092
Probing post-measurement entanglement without post-selection
Samuel J. Garratt, Ehud Altman

• Phys. Rev. B 107, 245132 (2023) https://arxiv.org/abs/2301.08268
  Nonlocality and entanglement in measured critical quantum Ising chains
  Zack Weinstein, Rohith Sajith, Ehud Altman, Samuel J. Garratt

• Phys. Rev. X 13, 021026 (2023) https://arxiv.org/abs/2207.09476
  Measurements conspire nonlocally to restructure critical quantum states
  Samuel J. Garratt, Zack Weinstein, Ehud Altman

• Phys. Rev. B 106, 054309 (2022) https://arxiv.org/abs/2202.10482
  Resonant energy scales and local observables in the many-body localized phase
  Samuel J. Garratt, Sthitadhi Roy

• Phys. Rev. A 106, 012441 (2022) https://arxiv.org/abs/2202.05132 

Quantifying information scrambling via Classical Shadow Tomography on Programmable Quantum Simulators

Max McGinley, Sebastian Leontica, Samuel J. Garratt, Jovan Jovanovic, Steven H. Simon

• Phys. Rev. B 104, 184203 (2021) https://arxiv.org/abs/2107.12387
  Local resonances and parametric level dynamics in the many-body localised phase
  S. J Garratt, Sthitadhi Roy, J. T. Chalker

• Phys. Rev. Lett. 127, 026802 (2021) https://arxiv.org/abs/2012.11580
  Many-body delocalisation as symmetry breaking
  S. J Garratt, J. T. Chalker

• Phys. Rev. X 11, 021051 (2021) https://arxiv.org/abs/2008.01697
  Local pairing of Feynman histories in many-body Floquet models
  S. J. Garratt, J. T. Chalker

• Phys. Rev. Lett. 126, 060402 https://arxiv.org/abs/2004.11363
  Many-body Decay of the Gapped Lowest Excitation of a Bose-Einstein Condensate
  Jinyi Zhang, Christoph Eigen, Wei Zheng, Jake A. P. Glidden, Timon A. Hilker, Samuel J. Garratt, Raphael Lopes, Nigel R. Cooper, Zoran Hadzibabic, Nir Navon

• Phys. Rev. B 101, 024413 (2020) https://arxiv.org/abs/1908.02271
  Goldstone modes in the emergent gauge fields of a frustrated magnet
  Samuel J. Garratt, J. T. Chalker

• Phys. Rev. A 99, 021601(R) (2019) https://arxiv.org/abs/1810.08195
  From single-particle excitations to sound waves in a box-trapped atomic Bose-Einstein condensate
  Samuel J. Garratt, Christoph Eigen, Jinyi Zhang, Patrik Turzák, Raphael Lopes, Robert P. Smith, Zoran Hadzibabic, Nir Navon

Research & before

• 2025 - now: Associate Research Scholar in Princeton 

• 2021 - 2025: Moore Fellowship in Berkeley, working with Ehud Altman and Joel Moore.

• 2017 - 2021: DPhil from Oxford, working with John Chalker. 

• 2013 - 2017: BA + MSci from Cambridge, with research in the group of Zoran Hadzibabic.