About

Saptarshi Chaudhuri is an assistant professor in the Department of Physics at Princeton University. He received his Ph.D. in physics from Stanford University in 2019 and his B.S. in physics from Caltech in 2013. His research interests include particle physics, cosmology, and astrophysics, with a special emphasis on axions and methods of dark matter detection. He has worked extensively with quantum sensors and superconducting detectors, such as parametric amplifiers, transition-edge sensors, and microwave kinetic inductance detectors. He is a recipient of several awards and honors including Stanford University’s Paul Kirkpatrick Award, given to graduate teaching assistants who have demonstrated excellence in the teaching of physics to undergraduates. He was a recipient of the Dicke Postdoctoral Fellowship from Princeton and the NASA Space Technology Research Fellowship for graduate work.

Research topics

• Computer Science
• Engineering
• Economics
• Ecology
• Environmental resource management
• Physics
• Quantum mechanics
• Mathematics
• Theoretical physics
• Environmental science
• Particle physics
• Environmental economics

Selected publications

• High-Q superconducting lumped-element resonators for low-mass axion searches

  Review of Scientific Instruments · 2026-02-01

  preprintOpen access

  Low-frequency superconducting lumped-element resonators have recently attracted significant attention in the context of axion dark matter searches. Here, we present the design and implementation of a fixed-frequency superconducting resonator operating near 250 kHz, possessing an inductor volume of ∼1 liter and achieving an unloaded quality factor Q ≈ 2.1 × 106. This resonator represents a significant improvement over the state of the art and informs the design of searches for low-mass axions.

  PublisherDOI

• Passive Pyrolytic Graphite Heat Switch for Sub-Kelvin Coolers

  SSRN Electronic Journal · 2025-01-01 · 1 citations

  preprintOpen accessSenior author
  PublisherDOI

• Near-quantum-limited subgigahertz <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><mml:mrow><mml:mi>Ti</mml:mi><mml:mi mathvariant="normal">N</mml:mi></mml:mrow></mml:math> kinetic inductance traveling-wave parametric amplifier operating in a frequency-translating mode

  Physical Review Applied · 2025-02-25 · 1 citations

  article

  We present the design and experimental characterization of a kinetic inductance traveling-wave parametric amplifier (KI-TWPA) for subgigahertz frequencies. KI-TWPAs amplify signals through mixing processes supported by the nonlinear kinetic inductance of a superconducting transmission line. The device described here uses a compactly meandered $\mathrm{Ti}\mathrm{N}$ microstrip transmission line to achieve the length needed to amplify subgigahertz signals. It is operated in a frequency-translating mode where the amplified signal tone is terminated at the output of the amplifier, and the idler tone at approximately 2.5 GHz is brought out of the cryostat. By varying the pump frequency, a gain of up to 22 dB was achieved in a tunable range from about 450 to 850 MHz. Using $\mathrm{Ti}\mathrm{N}$ as the nonlinear element allows for a reduction of the required pump power by roughly an order of magnitude relative to $\mathrm{Nb}\mathrm{Ti}\mathrm{N}$, which has been used for previous KI-TWPA implementations. This amplifier has the potential to enable high-sensitivity and high-speed measurements in a wide range of applications, such as quantum computing, astrophysics, and dark matter detection.

  PublisherDOI

• Electromagnetic modeling and science reach of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mtext>DMRadio-</mml:mtext><mml:msup><mml:mrow><mml:mi mathvariant="normal">m</mml:mi></mml:mrow><mml:mrow><mml:mn>3</mml:mn></mml:mrow></mml:msup></mml:mrow></mml:math>

  Physical review. D/Physical review. D. · 2025-09-02 · 1 citations

  articleOpen access

  <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:mrow><a:mtext>DMRadio-</a:mtext><a:msup><a:mrow><a:mi mathvariant="normal">m</a:mi></a:mrow><a:mrow><a:mn>3</a:mn></a:mrow></a:msup></a:mrow></a:math> is an experimental search for dark matter axions. It uses a solenoidal dc magnetic field to convert an axion dark-matter signal to an ac electromagnetic response in a coaxial copper pickup. The current induced by this axion signal is measured by dc SQUIDs. <d:math xmlns:d="http://www.w3.org/1998/Math/MathML" display="inline"><d:mrow><d:mtext>DMRadio-</d:mtext><d:msup><d:mrow><d:mi mathvariant="normal">m</d:mi></d:mrow><d:mrow><d:mn>3</d:mn></d:mrow></d:msup></d:mrow></d:math> is designed to be sensitive to Kim-Shifman-Vainshtein-Zakharov (KSVZ) and Dine-Fischler-Srednicki-Zhitnisky (DFSZ) QCD axion models in the 10–200 MHz (<g:math xmlns:g="http://www.w3.org/1998/Math/MathML" display="inline"><g:mrow><g:mn>41</g:mn><g:mtext> </g:mtext><g:mtext> </g:mtext><g:mi>neV</g:mi><g:mo>/</g:mo><g:msup><g:mi>c</g:mi><g:mn>2</g:mn></g:msup><g:mi>–</g:mi><g:mrow><g:mn>0.83</g:mn><g:mtext> </g:mtext><g:mtext> </g:mtext><g:mi mathvariant="normal">μ</g:mi><g:mi>eV</g:mi><g:mo>/</g:mo><g:msup><g:mi>c</g:mi><g:mn>2</g:mn></g:msup></g:mrow></g:mrow></g:math>) range, and to axions with <j:math xmlns:j="http://www.w3.org/1998/Math/MathML" display="inline"><j:msub><j:mi>g</j:mi><j:mrow><j:mi>a</j:mi><j:mi>γ</j:mi><j:mi>γ</j:mi></j:mrow></j:msub><j:mo>=</j:mo><j:msub><j:mi>g</j:mi><j:mrow><j:mi>a</j:mi><j:mi>γ</j:mi><j:mi>γ</j:mi><j:mo>,</j:mo><j:mrow><j:mi>DFSZ</j:mi></j:mrow></j:mrow></j:msub><j:mo stretchy="false">(</j:mo><j:mn>30</j:mn><j:mtext> </j:mtext><j:mtext> </j:mtext><j:mi>MHz</j:mi><j:mo stretchy="false">)</j:mo><j:mo>=</j:mo><j:mn>1.87</j:mn><j:mo>×</j:mo><j:msup><j:mn>10</j:mn><j:mrow><j:mo>−</j:mo><j:mn>17</j:mn></j:mrow></j:msup><j:mtext> </j:mtext><j:mtext> </j:mtext><j:msup><j:mrow><j:mi>GeV</j:mi></j:mrow><j:mrow><j:mo>−</j:mo><j:mn>1</j:mn></j:mrow></j:msup></j:math> over 5–30 MHz as an extended goal. In this work, we present the electromagnetic modeling of the response of the experiment to an axion signal over the full frequency range of <n:math xmlns:n="http://www.w3.org/1998/Math/MathML" display="inline"><n:mrow><n:mtext>DMRadio-</n:mtext><n:msup><n:mrow><n:mi mathvariant="normal">m</n:mi></n:mrow><n:mrow><n:mn>3</n:mn></n:mrow></n:msup></n:mrow></n:math>, which extends from the low-frequency, lumped-element limit to a regime where the axion Compton wavelength is only a factor of 2 larger than the detector size. With these results, we determine the live time and sensitivity of the experiment. The primary science goal of sensitivity to DFSZ axions across 30–200 MHz can be achieved with a <q:math xmlns:q="http://www.w3.org/1998/Math/MathML" display="inline"><q:mn>3</q:mn><q:mi>σ</q:mi></q:math> live scan time of 2.9 years.

  PublisherOA PDFDOI

• A Large Bore Conduction Cooled Superconducting Magnet for the Princeton Axion Search

  IEEE Transactions on Applied Superconductivity · 2025-01-30 · 1 citations

  articleOpen access

  Princeton University (PU) is designing and building a new experiment, called the Princeton Axion Search (PXS), that aims to discover (or exclude) Quantum Chromodynamics (QCD) axions in the 0.8–2 μeV mass range that are the cosmological dark matter. Core elements of the experiment are new, and in particular new to the search for axion dark matter. An essential component of the experiment is a 5 T superconducting magnet with a total bore volume of ∼500 L. The Princeton Plasma Physics Laboratory (PPPL), a Department of Energy (DOE) Laboratory managed by Princeton University, has the unique expertise and experimental facilities to design and construct such a solenoid magnet assembled with the cavity resonator for PXS. To support this, PPPL utilizes legacy ITER-Nb<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub>Sn conductors, along with its experimental facilities and expertises to design, build and test low-cost conduction-cooled superconducting solenoid magnets to be integrated into the axion detector. This paper discusses the various coil design and integration challenges in the large bore conduction cooled magnet in support of PXS. The proposed instrumental methods will help optimize the path to future and more ambitious axion searches at lower masses.

  PublisherDOI

• Passive pyrolytic graphite heat switch for sub-Kelvin coolers

  Cryogenics · 2025-04-16 · 1 citations

  articleOpen accessSenior author

  We describe a passive heat switch based on a commercial pyrolytic graphite sheet. Measurements of the thermal conductivity of the graphite are presented, confirming a large difference between room temperature and ≈4 K. The implementation of a graphite heat switch in a cryostat operating a 3 He/ 4 He sorption refrigerator is demonstrated. • Flexible pyrolytic graphite sheet is ideal for a passive heat switch. • The graphite's thermal conductivity is metal-like at room temperature but drops sharply at ≈4 K. • The pyrolytic graphite's thermal conductivity is ideal for use as a passive heat switch. • Graphite heat switches are easy to implement and use a widely available and affordable material.

  PublisherDOI

• Quantum metrology of low-frequency electromagnetic modes with frequency upconverters

  Physical Review Research · 2025-03-17 · 6 citations

  articleOpen access

  We present the RF Quantum Upconverter (RQU) and describe its application to quantum metrology of electromagnetic modes between dc and the very high frequency band (VHF) (<a:math xmlns:a="http://www.w3.org/1998/Math/MathML"><a:mrow><a:mo>≲</a:mo><a:mn>300</a:mn></a:mrow></a:math> MHz). The RQU uses a Josephson interferometer made up of superconducting loops and Josephson junctions to implement a parametric interaction between a low-frequency electromagnetic mode (between dc and VHF) and a mode in the microwave C Band (<b:math xmlns:b="http://www.w3.org/1998/Math/MathML"><b:mrow><b:mo>∼</b:mo><b:mn>5</b:mn></b:mrow></b:math> GHz), analogous to the radiation pressure interaction between electromagnetic and mechanical modes in cavity optomechanics. We analyze RQU performance with quantum amplifier theory and show that the RQU can operate as a quantum-limited op-amp in this frequency range. It can also use nonclassical measurement protocols equivalent to those used in cavity optomechanics, including back-action evading (BAE) measurements, sideband cooling, and two-mode squeezing. These protocols enable experiments using dc VHF electromagnetic modes as quantum sensors with sensitivity better than the standard quantum limit (SQL). We demonstrate signal upconversion from low frequencies to the microwave C band using an RQU and show a phase-sensitive gain (extinction ratio) of <c:math xmlns:c="http://www.w3.org/1998/Math/MathML"><c:mrow><c:mn>46.9</c:mn><c:mspace width="0.28em"/><c:mi>dB</c:mi></c:mrow></c:math>, which is a necessary step towards the realization of full BAE.

  PublisherDOI

• Noise limits for dc SQUID readout of high-<i>Q</i> resonators below 300 MHz

  Journal of Applied Physics · 2025-09-04

  articleOpen access

  We present the limits on noise for the readout of cryogenic high-Q resonators using dc Superconducting Quantum Interference Devices (SQUIDs) below 300 MHz. This analysis uses realized first-stage SQUIDs (previously published), whose performance is well described by Tesche–Clarke (TC) theory, coupled directly to the resonators. We also present data from a prototype second-stage dc SQUID array designed to couple to this first-stage SQUID as a follow-on amplifier with high system bandwidth. This analysis is the first full consideration of dc SQUID noise performance referred to a high-Q resonator over this frequency range and is presented relative to the standard quantum limit. We include imprecision, backaction, and backaction–imprecision noise correlations from TC theory, the noise contributed by the second-stage SQUIDs, wiring, and preamplifiers, and optimizations for both on-resonance measurements and off-resonance scan sensitivity. This architecture has modern relevance due to the increased interest in axion searches and the requirements of the DMRadio-m3 axion search, which uses dc SQUIDs in this frequency range.

  PublisherDOI

• A Near Quantum Limited Sub-GHz TiN Kinetic Inductance Traveling Wave Parametric Amplifier Operating in a Frequency Translating Mode

  arXiv (Cornell University) · 2024-06-01 · 2 citations

  preprintOpen access

  We present the design and experimental characterization of a kinetic-inductance traveling-wave parametric amplifier (KI-TWPA) for sub-GHz frequencies. KI-TWPAs amplify signals through nonlinear mixing processes supported by the nonlinear kinetic inductance of a superconducting transmission line. The device described here utilizes a compactly meandered TiN microstrip transmission line to achieve the length needed to amplify sub-GHz signals. It is operated in a frequency translating mode where the amplified signal tone is terminated at the output of the amplifier, and the idler tone at approximately 2.5~GHz is brought out of the cryostat. By varying the pump frequency, a gain of up to 22 dB was achieved in a tunable range from about 450 to 850~MHz. Use of TiN as the nonlinear element allows for a reduction of the required pump power by roughly an order of magnitude relative to NbTiN, which has been used for previous KI-TWPA implementations. This amplifier has the potential to enable high-sensitivity and high-speed measurements in a wide range of applications, such as quantum computing, astrophysics, and dark matter detection.

  PublisherOA PDFDOI

• Optimizing Synchronization Signal Block Transmissions for Sum-Rate Maximization in Sub-Connected Hybrid Beamforming Systems

  2024-12-15

  articleSenior author

  Fifth-generation millimeter wave (mmWave) systems rely on sub-connected (SC) hybrid beamforming architecture due to low power consumption and reduced hardware complexity. These systems require directional beamforming to establish communication between the base station (BS) and user equipment (UE). Typically, the communication between BS and UE occurs in two phases. In the first namely initial access (IA) phase, BS utilizes spatial beam search using synchronization signal (SS) blocks for link establishment and is followed by data transmission in the second phase. As per the 3GPP standard for 5G NR systems, existing approaches utilize a maximum IA duration of 5ms corresponding to the transmission of 64 SS blocks for beam search. The maximum transmission of SS blocks results in a significant delay in data transmission to the user. This work proposes an optimized value of the number of SS block transmissions to achieve a higher sum-rate in an SC hybrid mmWave system. Simulation results demonstrate that an optimized value of SS block transmission results in faster user discovery and yields more time for data transmission. This in turn results in an improved performance of the SC hybrid beamforming systems in terms of enhanced sum-rate capacity and reduced initial beam acquisition time.

  PublisherDOI

Frequent coauthors

• K. D. Irwin

  57 shared

• Debabrata Das

  International Institute of Information Technology Bangalore

  19 shared

• Peter W. Graham

  Kavli Institute for Particle Astrophysics and Cosmology

  18 shared

• Johannes Hubmayr

  National Institute of Standards and Technology

  18 shared

• Clint Bockstiegel

  European Organization for Nuclear Research

  18 shared

• Stephen Kuenstner

  18 shared

• C Dawson

  University of Maryland Medical System

  16 shared

• Betty Young

  Santa Clara University

  16 shared

Labs

• Saptarshi Chaudhuri LabPI

Education

• Postdoctoral Researcher, Physics

  Stanford University

  2020

• Ph.D., Physics

  Stanford University

  2019

• B.S., Physics

  California Institute of Technology

  2013

Awards & honors

• Paul Kirkpatrick Award