Technique - (18) Squeezed microwave / quantum-limited amplification

Type: Experimental

Description: Josephson parametric amplifiers and SQUIDs operating at or below the standard quantum limit.

Department(s)/lab(s): School of Electrical Engineering and Telecommunications | Pla Quantum Spin Control and Sensing Laboratory @ UNSW
Summary:

Pla is the strongest single match in this cohort for a candidate whose background is sensitivity-limited spin detection. His laboratory does inductively-detected electron spin resonance at millikelvin using high-quality-factor superconducting microresonators, read out through Josephson and travelling-wave parametric amplifiers operating at the quantum limit of added noise. The result is ESR sensitivity improved by many orders of magnitude over commercial spectrometers β€” the group's stated target is single-spin inductive detection β€” and, in parallel, the development of near-ideal degenerate parametric amplifiers and squeezed microwave states as the readout resource that makes it possible. Applications explicitly include chemistry and biology, where the goal is to do EPR on samples far too small for a conventional spectrometer. Positioned against the established body of NV-ensemble quantum sensing work β€” DEER, nanoscale NMR and T1 relaxometry protocols operating at pT/sqrt(Hz) field sensitivity β€” this is the microwave-inductive route to the same destination: where an NV ensemble reaches pT/sqrt(Hz) by optical readout of many spins, Pla reaches comparable or better spin sensitivity by making the microwave detection chain quantum-limited, and the DEER and dynamical-decoupling sequences are shared verbatim. Preferred attribute present in the strongest form: cutting-edge sensitivity, not device fabrication, is the object.

Department(s)/lab(s): Physics / Niels Bohr Institute | QUANTOP – Quantum Optics Center (Polzik Lab) @ UCPH
Summary:

Eugene Polzik's QUANTOP centre uses hot and ultracold atomic spin ensembles and mechanical membranes to generate squeezed, entangled, and single-photon states for quantum sensing and communication. Key directions include: (1) atomic magnetometry and electromagnetic induction imaging for biomedical applications (MEG/MCG-quality sensors); (2) entanglement between a macroscopic mechanical oscillator and an atomic spin ensemble; (3) quantum memory for light; (4) back-action-evading measurement schemes beyond the SQL; and (5) optical preamplification for MRI. QUANTOP heads the Copenhagen Center for Biomedical Quantum Sensing (CBQS), targeting quantum-enhanced disease diagnostics.

Department(s)/lab(s): Department of Physics, 1st Institute of Physics | Pop Group - Superconducting Quantum Circuits (1. Physikalisches Institut) @ Stuttgart
Summary:

Pop's group builds superconducting quantum circuits from high-kinetic-inductance materials, above all granular aluminium, and uses them as detectors. The distinctive capability is single-microwave-photon detection and QND photon counting with superinductor-based devices -- an extremely low dark-count, quantum-limited receiver in the GHz band -- plus fluxonium-type qubits, quantum-limited and travelling-wave parametric amplification, and studies of quasiparticle and noise mechanisms that set coherence limits. The direct sensing payoff is dark-matter search: a photon counter that beats the standard quantum limit lets a haloscope integrate far faster than an amplifier-based readout. Relative to the established NV-ensemble quantum-sensing playbook (DEER, nanoscale NMR, T1 relaxometry at pT/sqrt(Hz) ensemble sensitivity), this is the microwave/superconducting counterpart to an NV ensemble -- same objective (detect an absurdly weak field), different physical platform and roughly opposite temperature regime. A recent addition to Stuttgart's 1st Institute of Physics, so the lab is being built out now, which usually means unusual latitude for a postdoc.

Department(s)/lab(s): School of Physics | Quantum Nanoscience Laboratory @ USyd
Summary:

Reilly's Quantum Nanoscience Laboratory works on the interface between quantum devices and the classical control hardware needed to run them at scale β€” custom VLSI CMOS operating below 100 mK, high-bandwidth dispersive readout, and cryogenic microwave engineering β€” a programme built up during his long association with Microsoft's quantum effort. A distinct and directly relevant second thread is the manipulation of spin states in nanoparticles for new imaging modalities in medicine: hyperpolarisation and spin-state engineering of nanoparticle contrast agents, which is quantum control applied to MRI. Positioned against the established body of NV-ensemble quantum sensing work β€” DEER, nanoscale NMR and T1 relaxometry protocols operating at pT/sqrt(Hz) field sensitivity β€” the cryo-CMOS readout chain he builds is exactly the enabling technology that would let a pT/sqrt(Hz) spin-ensemble sensor be multiplexed into an array rather than run one channel at a time; and the nanoparticle-MRI thread is an independent route into biological spin sensing. Large group, strong engineering culture, significant industry entanglement.

Department(s)/lab(s): Physics / Niels Bohr Institute | Quantum Optomechanics Group (Schliesser Lab) @ UCPH
Summary:

Albert Schliesser's group engineers ultracoherent phononic crystal membrane resonators with dissipation-dilution Q>10^9 and uses them for quantum optomechanics: ground-state cooling, back-action-evading measurement, optical quantum memory for single photons, and microwave-optical quantum transduction. Recent work has demonstrated a soft-clamped topological phononic waveguide (Nature 2025) and scanning force microscopy below the standard quantum limit. The group bridges fundamental quantum physics with novel sensors for electromagnetic fields and forces, and mechanical interfaces for hybrid quantum networks.

Department(s)/lab(s): Physics and Electrical Engineering & Computer Sciences | Siddiqi Quantum Nanoelectronics Laboratory (QNL) @ UCB
Summary:

Siddiqi's Quantum Nanoelectronics Laboratory develops superconducting quantum circuits and near-quantum-limited parametric amplifiers for qubit readout, quantum feedback, and quantum-enhanced sensing, and directs cross-campus quantum information efforts at Berkeley and LBNL.

Department(s)/lab(s): Physics (Astrophysics Sub-department) | Superconducting Quantum Detectors Group @ Oxford
Summary:

Tan leads the Superconducting Quantum Detectors group, holding ERC Starting and Consolidator Grants. Two main research pillars: (1) Quantum-limited SIS mixer development β€” pushing THz SIS heterodyne receivers above the Nb gap (~700 GHz) using NbTiN/NbN films for next-generation ALMA wideband sensitivity upgrade (Band 9) and large-format focal-plane mixer arrays for JCMT/SMA; (2) Superconducting parametric amplifiers (TWPAs) β€” fabricating kinetic-inductance and Josephson-junction TWPAs achieving near-quantum-limited broadband noise performance from microwave to THz, with applications to dark matter/axion searches (ABRACADABRA/prototype cavity haloscope), quantum computing qubit readout, and CMB-grade receivers. Group is transitioning TWPA fabrication in-house using Beecroft Building cleanroom. ERC Consolidator Grant awarded 2024.

Department(s)/lab(s): Physics – Institute for Quantum Electronics / PSI | Experimental Quantum Engineering Group (Xu) @ ETH Zurich
Summary:

Xu leads the Experimental Quantum Engineering group with a joint ETH–PSI appointment. Research directions: (1) Superconducting circuit quantum sensing β€” using qubits-as-sensors for detecting weak microwave signals beyond standard quantum limits, quantum non-demolition readout of photon fields; (2) Quantum error correction enabled sensing β€” integrating bosonic codes (cat qubits, binomial codes) into sensing protocols; (3) Quantum acoustics β€” coupling superconducting qubits to surface acoustic wave (SAW) resonators for hybrid quantum sensing; (4) Novel quantum hardware at PSI β€” leveraging PSI's infrastructure for cryogenic device fabrication and testing. Connected to the ETH–PSI Quantum Computing Hub.