About

Ashok Ajoy is an Assistant Professor of Chemistry at the University of California, Berkeley. Born in 1987, he earned his B.E. and M.S. degrees from BITS-Pilani, India, in 2010, and completed his Ph.D. at MIT in 2016 under the supervision of Prof. Paola Cappellaro. He then conducted postdoctoral research at the University of California, Berkeley, from 2016 to 2020 with Prof. Alex Pines. His research focuses on physical chemistry, specifically nanoscale NMR spectroscopy, targetable spin hyperpolarization agents, quantum sensing, and quantum computing with spins. He develops innovative methods to enhance NMR signals through optical-spin hyperpolarization and aims to enable NMR spectroscopy within natural sample environments by deploying nanoscale spatial resolution probes. His work includes the development of NMR quantum microscopy, which leverages quantum sensors for high-resolution chemical analysis at the nanoscale, and the creation of portable NMR and MRI devices that combine the specificity of NMR with low-cost laser technology. Additionally, Ajoy's research explores the fragility of quantum systems as sensors in real-world environments, contributing to quantum computing and quantum metrology. His investigations into nanoscale spin dynamics provide insights into phenomena such as spin localization, thermalization, and spin diffusion, with potential applications in spintronic devices and quantum information processing.

Research topics

• Condensed matter physics
• Materials science
• Physics
• Nuclear magnetic resonance
• Atomic physics
• Nanotechnology
• Optoelectronics
• Quantum mechanics
• Molecular physics

Selected publications

• Out-of-time-order correlators bridge classical transport and quantum dynamics

  AIP Publishing · 2026-04-01

  otherOpen access

  The out-of-time-order correlator (OTOC) has emerged as a central tool for quantifying decoherence across wide-ranging physical platforms. Here we demonstrate its direct measurement in a classical ensemble using nuclear magnetic resonance (NMR) with a modulated gradient spin echo (MGSE) sequence and extend the method into a multidimensional correlation to track exchange phenomena. Position is encoded through magnetic field gradients and momentum through the velocity autocorrelation function, enabling experimental access to OTOCs for proton motion confined within the self-similar lattice of the metal-organic framework MOF-808. Here, water confined to specified geometries within the MOF pores gives rise to spatially distinct diffusive eigenmodes with characteristic relative entropies. We demonstrate that periodic radiofrequency (rf) driving combined with gradient modulation yields entropy evolution through the selection of distinct diffusion modes. Frequency-resolved diffusion spectra connect these entropy dynamics to classical heat exchange laws, revealing how operational features of quantum systems are mirrored in confined, macroscopic spin ensembles.

  PublisherDOI

• Out-of-time-order correlators bridge classical transport and quantum dynamics

  AIP Publishing · 2026-04-01

  otherOpen access

  The out-of-time-order correlator (OTOC) has emerged as a central tool for quantifying decoherence across wide-ranging physical platforms. Here we demonstrate its direct measurement in a classical ensemble using nuclear magnetic resonance (NMR) with a modulated gradient spin echo (MGSE) sequence and extend the method into a multidimensional correlation to track exchange phenomena. Position is encoded through magnetic field gradients and momentum through the velocity autocorrelation function, enabling experimental access to OTOCs for proton motion confined within the self-similar lattice of the metal-organic framework MOF-808. Here, water confined to specified geometries within the MOF pores gives rise to spatially distinct diffusive eigenmodes with characteristic relative entropies. We demonstrate that periodic radiofrequency (rf) driving combined with gradient modulation yields entropy evolution through the selection of distinct diffusion modes. Frequency-resolved diffusion spectra connect these entropy dynamics to classical heat exchange laws, revealing how operational features of quantum systems are mirrored in confined, macroscopic spin ensembles.

  PublisherDOI

• Out-of-time-order correlators bridge classical transport and quantum dynamics

  The Journal of Chemical Physics · 2026-04-01

  articleOpen access

  The out-of-time-order correlator (OTOC) has emerged as a central tool for quantifying decoherence across wide-ranging physical platforms. Here, we demonstrate its direct measurement in a classical ensemble using nuclear magnetic resonance with a modulated gradient spin echo sequence and extend the method into a multidimensional correlation to track exchange phenomena. Position is encoded through magnetic field gradients and momentum through the velocity autocorrelation function, enabling experimental access to OTOCs for proton motion confined within the self-similar lattice of the metal-organic framework MOF-808. Here, water confined to specified geometries within the MOF pores gives rise to spatially distinct diffusive eigenmodes with characteristic relative entropies. We demonstrate that periodic radio frequency driving combined with gradient modulation yields entropy evolution through the selection of distinct diffusion modes. Frequency-resolved diffusion spectra connect these entropy dynamics to classical heat exchange laws, revealing how operational features of quantum systems are mirrored in confined, macroscopic spin ensembles.

  PublisherDOI

• Supplemental Material

  AIP Publishing · 2026-04-01

  articleOpen access

  This PDF file includes: Supplementary Text Figures S1-S2 Supplementary References

  PublisherDOI

• Supplemental Material

  AIP Publishing · 2026-04-01

  articleOpen access

  This PDF file includes: Supplementary Text Figures S1-S2 Supplementary References

  PublisherDOI

• Sensing with discrete time crystals

  Nature Physics · 2026-02-23 · 2 citations

  preprintOpen accessSenior authorCorresponding

  Abstract Prethermal discrete time crystals are non-equilibrium states of matter with long-range spatiotemporal order and a subharmonic response stabilized by many-body interactions under periodic driving. The robustness of time-crystalline order to perturbations in the drive protocol makes these systems attractive for quantum sensing. Here we exploit the sensitivity of prethermal discrete time crystal order to deviations in its order parameter to implement the frequency-selective detection of time-varying magnetic fields in a system of strongly driven, dipolar-coupled 13 C nuclear spins in a diamond. Incorporating an oscillating field into the time crystal dynamics extends its lifetime exponentially, producing a sharp resonant response in the order parameter. The sensor linewidth is set by the time crystal lifetime alone, as strong interspin interactions help stabilize the time-crystalline order. The device operates in the 0.5–50-kHz range—a challenging frequency regime for sensors based on atomic vapour or electronic spins—and achieves competitive sensitivity. The sensing principle we demonstrate is robust to drive errors and sample inhomogeneities, and is applicable across a range of physical platforms including superconducting circuits, neutral atoms and trapped ions.

  PublisherOA PDFDOI

• High sensitivity pressure and temperature quantum sensing in pentacene-doped p-terphenyl single crystals

  Nature Communications · 2025-11-26 · 6 citations

  articleOpen accessSenior authorCorresponding

  Quantum sensors' responsiveness to their physical environment enables detection of variables such as temperature (T), pressure (P), and strain. We present a molecular platform for PT sensing using para-terphenyl crystals doped with pentacene (PDP), leveraging optically detected magnetic resonance (ODMR) of photoexcited triplet electron spins. We observe maximal frequency variations of df/dP=1.8 MHz/bar from 0-8 bar and df/dT=247 kHz/K from 79-330 K, over 1200 times and threefold greater, respectively, than those seen with nitrogen-vacancy centers in diamond and > 85-fold greater pressure sensitivity over the previous record. Density functional theory calculations indicate picometer-level PT-induced molecular orbital shifts are measurable via ODMR. PDP offers additional advantages including high sensor doping levels, narrow ODMR linewidths, high contrast, and low-cost single crystal growth. Overall, this work reports low-cost, optically-interrogated PT sensors and lays the foundation for increased versatility of quantum sensors through synthetic molecular design.

  PublisherOA PDFDOI

• Quantum Sensing of Paramagnetic Analytes by Nanodiamonds in Levitated Microdroplets and Aqueous Solutions

  ChemRxiv · 2025-06-09

  preprintOpen access

  Nanodiamonds (ND) hosting negatively charged nitrogen-vacancy (NV-) color centers have received attention for applications in magnetic field, electric field, chemical, and bio-sensing. The versatility of these probes is their excellent room-temperature optical and spin properties, along with their small size, functionalized surfaces and resistance to bleaching, making them ideal as nanoscopic sensors in picoliter volumes (e.g. single cells, but also microcompartments and aerosols). For quantitative ND-NV- sensing of paramagnetic analytes in such contexts, however, there remains an incomplete understanding of how factors related to the aqueous phase environment control detection efficiency. To address this, optically detected magnetic resonance (ODMR) is measured in bulk macroscale solutions and single levitated microdroplets as a function of Gd+3 concentration (340 nM to 1.5 mM), nanodiamond size, pH, competitor ions, and ligands. The ODMR response to [Gd+3] is found to be nonlinear, and pH, ND and sample volume dependent; indicating the detection of Gd+3 requires efficient adsorption of the analyte to the diamond surface. Langmuir adsorption isotherms embedded in a quantitative photophysical model links the ODMR response to adsorption thermodynamics of Gd+3. The equilibrium constant for Gd+3 adsorption to a carboxylated ND surface is determined to be (1 ± 0.5) x 105 M-1 corresponding to a free energy of adsorption of (-28 ± 1) kJ/mol. These results provide general insight into how complex aqueous and microscale environments impact nanodiamond based quantum sensing modalities, and portend their application as quantitative chemical sensors in microenvironments.

  PublisherOA PDFDOI

• Cryogenic Field-Cycling Instrument for Optical Nmr Hyperpolarization Studies

  SSRN Electronic Journal · 2025-01-01

  preprintOpen accessSenior author
  PublisherDOI

• Observation of constructive interference at the edge of quantum ergodicity

  Nature · 2025-10-22 · 16 citations

  articleOpen access

  The dynamics of quantum many-body systems is characterized by quantum observables that are reconstructed from correlation functions at separate points in space and time1–3. In dynamics with fast entanglement generation, however, quantum observables generally become insensitive to the details of the underlying dynamics at long times due to the effects of scrambling. To circumvent this limitation and enable access to relevant dynamics in experimental systems, repeated time-reversal protocols have been successfully implemented4. Here we experimentally measure the second-order out-of-time-order correlators (OTOC(2))5–18 on a superconducting quantum processor and find that they remain sensitive to the underlying dynamics at long timescales. Furthermore, OTOC(2) manifests quantum correlations in a highly entangled quantum many-body system that are inaccessible without time-reversal techniques. This is demonstrated through an experimental protocol that randomizes the phases of Pauli strings in the Heisenberg picture by inserting Pauli operators during quantum evolution. The measured values of OTOC(2) are substantially changed by the protocol, thereby revealing constructive interference between Pauli strings that form large loops in the configuration space. The observed interference mechanism also endows OTOC(2) with high degrees of classical simulation complexity. These results, combined with the capability of OTOC(2) in unravelling useful details of quantum dynamics, as shown through an example of Hamiltonian learning, indicate a viable path to practical quantum advantage. Experimental measurements of high-order out-of-time-order correlators on a superconducting quantum processor show that these correlators remain highly sensitive to the quantum many-body dynamics in quantum computers at long timescales.

  PublisherOA PDFDOI

Frequent coauthors

• Carlos A. Meriles

  City College of New York

  79 shared

• Jeffrey A. Reimer

  University of California, Berkeley

  66 shared

• Emanuel Druga

  64 shared

• Alexander Pines

  University of California, Berkeley

  62 shared

• Paola Cappellaro

  Massachusetts Institute of Technology

  48 shared

• Raffi Nazaryan

  University of California, Berkeley

  41 shared

• Kristina Liu

  Kaiser Permanente San Francisco Medical Center

  36 shared

• Dieter Suter

  TU Dortmund University

  30 shared