Technique - (27) Electron paramagnetic resonance (EPR)

Type: Experimental

Description: Spectroscopy of unpaired electron spins; used for structural biology, spin-label distance measurements, and quantum sensing.

Department(s)/lab(s): Department of Materials (D-MATL) | Magnetism and Interface Physics Group (Gambardella) @ ETH Zurich
Summary:

Gambardella leads the Magnetism and Interface Physics group at ETH D-MATL. Research directions: (1) Scanning probe magnetometry โ€” using NV-center cantilevers (collaboration with Degen) and magneto-optical Kerr microscopy to image spin textures (skyrmions, domain walls) in thin-film heterostructures with sub-100 nm resolution; (2) Spin-orbit torques โ€” current-induced magnetization switching via interfacial spin-orbit coupling; spin Hall and Rashba effects for spintronic devices; (3) Single-atom magnetism โ€” STM and X-ray absorption for element-specific orbital and spin moments of individual atoms on surfaces; (4) XMCD at synchrotron โ€” quantitative element-specific magnetic spectroscopy. Quantum sensing angle: spin-orbit driven phenomena, high-resolution magnetic imaging.

Department(s)/lab(s): School of Chemistry | Giansiracusa Lanthanoid Magnetism Group @ UMelb
Summary:

Giansiracusa is an early-career PI (ARC DECRA) working on ytterbium and other lanthanoid single-molecule magnets, combining synthesis, magnetometry and ab initio electronic-structure calculation to understand and engineer magnetic anisotropy and spin relaxation. The stated aim of his DECRA is to move Yb-based single-molecule magnets toward real-world application, which in practice means qubit and sensor use cases where long coherence at accessible temperatures matters. Positioned against the established body of NV-ensemble quantum sensing work โ€” DEER, nanoscale NMR and T1 relaxometry protocols operating at pT/sqrt(Hz) field sensitivity โ€” the relaxation-time engineering problem he is attacking is the molecular analogue of the T1/T2 optimisation that sets pT/sqrt(Hz) performance in NV ensembles. Small, new group; a candidate would have unusual latitude but limited infrastructure.

Department(s)/lab(s): Chemistry | Han Laboratory @ Northwestern
Summary:

The Han Lab (Chemistry, joined fall 2023) develops quantum sensing tools rooted in electron and nuclear spin physics for life-science applications. Directions: (1) DNP-enhanced NMR quantum sensing using coupled electron-nuclear spin clusters โ€” designing novel biradical and multi-spin systems achieving 700-fold ยนยณC signal enhancement at 14.1 T via P1 center clusters in HPHT diamond (exchange coupling >100 MHz); aiming for in-cell NMR with sensitivity to track water dynamics in a single cell; (2) High-field pulsed EPR at 240 GHz / 8.6 T: time-resolved Gd-Gd EPR (TiGGER) for tracking inter-residue distances during protein functional cycles in solution with sub-nm resolution; rapid-scan field-domain EPR development; (3) Integration of DNP/EPR with nanodiamond-based quantum sensors: coupled electron-nuclear spin cluster design for long-range quantum sensing in biological environments, bridging conventional NMR/EPR and NV-center-based quantum sensing. Han directs the EPR/DNP component of IMSERC (Northwestern's core facility) and brought three new EPR spectrometers and a 600 MHz DNP-NMR system.

Department(s)/lab(s): Department of Chemistry, Institute of Inorganic and Analytical Chemistry | AK Heinze - Molecular Photophysics @ JGU
Summary:

Heinze designs earth-abundant luminescent metal complexes -- the 'molecular ruby' (Cr(III)) family and its Mo(III) NIR-II-emitting analogues -- and studies their excited-state dynamics with time-resolved luminescence, ultrafast spectroscopy and EPR, in collaboration with spin-spectroscopy groups including van Slageren at Stuttgart. Applications targeted include optical sensing (oxygen, pressure, temperature), NIR-II imaging in the tissue-transparency window, and photocatalysis. Relative to the established NV-ensemble quantum-sensing playbook (DEER, nanoscale NMR, T1 relaxometry at pT/sqrt(Hz) ensemble sensitivity), this is a dye/label-based sensing inclusion rather than a spin-defect one: the emphasis is on engineering the emitter's photophysics so that lifetime and intensity report on the local environment, which is directly comparable to nanodiamond thermometry/relaxometry but at the molecular scale.

Department(s)/lab(s): Chemistry | Hoffman ENDOR Spectroscopy Group @ Northwestern
Summary:

Hoffman develops and applies electron-nuclear double resonance (ENDOR) spectroscopy -- a combination of EPR and NMR -- to resolve individual hyperfine-coupled nuclei at metalloenzyme active sites with atomic-scale precision, work that has revealed mechanisms of nitrogenase nitrogen fixation, radical-SAM enzyme catalysis, and copper/methane monooxygenase chemistry. The technique pushes magnetic-resonance spectroscopic resolution well past what conventional EPR can resolve, in a manner methodologically continuous with molecular spin-qubit sensing.

Department(s)/lab(s): School of Physics | Electronic and Condensed Matter Physics Group (McCallum) @ UMelb
Summary:

McCallum works on the materials and detector physics of donor qubits in silicon and colour centres in diamond and silicon carbide: defect engineering by ion implantation and annealing, characterisation of the resulting spin coherence, and โ€” most relevant to a sensing postdoc โ€” the development of superconducting and semiconductor detectors capable of registering single implanted ions with near-unit efficiency, which is what turns implantation from a statistical process into a deterministic one. He also works on near-surface colour centres, where surface termination and Fermi-level control set the achievable coherence. Positioned against the established body of NV-ensemble quantum sensing work โ€” DEER, nanoscale NMR and T1 relaxometry protocols operating at pT/sqrt(Hz) field sensitivity โ€” his group supplies the near-surface, coherence-optimised spin ensembles that DEER, nanoscale NMR and T1-relaxometry protocols at pT/sqrt(Hz) sensitivity actually depend on.

Department(s)/lab(s): School of Physics | McCamey Spin Physics and ODMR Laboratory @ UNSW
Summary:

McCamey is, for a candidate coming from NV ensemble sensing, the single most methodologically adjacent PI at UNSW. His laboratory does optically and electrically detected magnetic resonance on spins that are not defects in diamond: photogenerated spin-correlated radical pairs, triplet excitons in organic semiconductors, singlet-fission intermediates, and molecular spin systems. The instrumentation is the same toolkit โ€” pulsed EPR, ODMR, dynamical decoupling, relaxometry โ€” applied to systems where the spin is created by light and reports on chemistry. He directs the UNSW node of ARC Exciton Science. Positioned against the established body of NV-ensemble quantum sensing work โ€” DEER, nanoscale NMR and T1 relaxometry protocols operating at pT/sqrt(Hz) field sensitivity โ€” his group runs precisely those pulse sequences (Hahn echo, DEER, relaxometry) on a different spin species, and radical-pair spin chemistry is one of the few plausible mechanisms by which biology could be genuinely quantum โ€” which makes this a strong landing spot for someone wanting to keep the NV skill set but change the physical system. Preferred attributes present: sensitivity-limited spin measurement, quantum-biology relevance.

Department(s)/lab(s): Chemistry โ€“ National Electron Paramagnetic Resonance Facility | National EPR Facility / McInnes Group @ Manchester
Summary:

McInnes leads the National EPR Facility at Manchester (Europe's broadest EPR suite) and researches molecular spin qubits. Research directions: (1) Pulsed EPR spectroscopy of molecular spin systems โ€” Hahn echo, ESEEM, ENDOR, DEER for structural and electronic characterization of inorganic and organometallic complexes; (2) Molecular spin qubits โ€” [Cu(mnt)2]ยฒโป and related molecules as candidate qubits; measuring coherence times and investigating decoherence mechanisms; (3) Multi-qubit molecular registers โ€” using exchange interactions for two-qubit gates within a molecule; (4) Magnetic sensing applications โ€” molecular systems for magnetic field sensing below the diffraction limit. Partner of NPL M4Q EPSRC Network for Materials for Quantum.

Department(s)/lab(s): School of Electrical Engineering and Telecommunications | Fundamental Quantum Technologies Laboratory (Morello) @ UNSW
Summary:

Morello heads the Fundamental Quantum Technologies Laboratory and is the person who first read out the spin of a single electron, and then a single nucleus, in silicon. Current directions: high-spin donors (antimony-123, with eight nuclear levels) used as qudits and as sensors of local strain and electric field; nuclear acoustic resonance, in which a strain wave rather than a magnetic field drives the nuclear spin; engineered decoherence experiments as tests of quantum foundations; and precision tomography of multi-qubit donor registers. The group's donors are among the longest-coherence solid-state spins known (seconds for nuclei). Positioned against the established body of NV-ensemble quantum sensing work โ€” DEER, nanoscale NMR and T1 relaxometry protocols operating at pT/sqrt(Hz) field sensitivity โ€” a single-donor nuclear spin in silicon is functionally an NV centre with better coherence and worse readout: the same DEER, dynamical-decoupling and nuclear-register protocols apply, and the group's high-spin qudit work is aimed at exactly the multi-level sensing enhancements that the NV community is now chasing. Preferred attribute present: sensitivity and coherence, not fabrication, are the limiting variables here.

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 โ€” the group's stated target is single-spin inductive detection โ€” 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 โ€” DEER, nanoscale NMR and T1 relaxometry protocols operating at pT/sqrt(Hz) field sensitivity โ€” 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.