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 Chemistry, Institute of Inorganic and Analytical Chemistry | AK Rentschler - Molecular Magnetism @ JGU
Summary:

Rentschler's group synthesizes and characterizes molecular magnetic materials: single-molecule magnets, spin-crossover complexes and polynuclear coordination clusters, with magnetic anisotropy engineered through ligand-field design and characterized by SQUID magnetometry, EPR and ab-initio calculations. The overlap with this search is the molecular-qubit angle -- these are the same chemical objects being pursued elsewhere as optically or electrically addressable spin qubits and as molecular quantum sensors. Relative to the established NV-ensemble quantum-sensing playbook (DEER, nanoscale NMR, T1 relaxometry at pT/sqrt(Hz) ensemble sensitivity), the value here is chemical: designed spin systems with tunable coherence and anisotropy, rather than defects in a host crystal. Borderline-strong inclusion; the group is chemistry-first, so a physicist postdoc would bring the spin-readout side.

Department(s)/lab(s): Chemistry | Roessler EPR Spectroscopy Group @ Imperial
Summary:

Roessler uses continuous-wave and pulsed EPR/ENDOR spectroscopy to probe paramagnetic metal centres and radical intermediates in catalytic and bioinorganic systems, work that overlaps with the use of molecular spin centres as candidate EPR-addressable qubits/sensors.

Department(s)/lab(s): School of Physics | Rogge Single Dopant Spectroscopy Group @ UNSW
Summary:

Rogge (formerly Delft) works on the spectroscopy of individual dopant atoms in silicon: using transport, STM and microwave spectroscopy to read out the orbital, valley and spin structure of single donors and acceptors, including their coupling to strain, electric fields and each other. The group has mapped the wavefunctions of individual dopants and used acceptor spin-orbit coupling for electric-field-driven spin control. This is single-quantum-object measurement rather than device engineering. Positioned against the established body of NV-ensemble quantum sensing work — DEER, nanoscale NMR and T1 relaxometry protocols operating at pT/sqrt(Hz) field sensitivity — single-donor spectroscopy is the silicon analogue of single-NV work: the same questions about coherence, bath engineering and readout fidelity that fix pT/sqrt(Hz) ensemble performance appear here in a platform where the sensor can be placed with atomic precision and interrogated electrically rather than optically.

Department(s)/lab(s): Institute of Physical Chemistry | Tesi Group - Optically Addressable Molecular Spins @ Stuttgart
Summary:

Tesi leads an independent group at Stuttgart's Institute of Physical Chemistry working on optically addressable molecular spin systems -- the effort to reproduce the NV centre's defining trick (optical initialization and readout of a spin) in a designed molecule, where chemistry rather than crystal growth sets the properties. Work spans photogenerated spin-correlated radical pairs, ODMR on molecular chromophore-radical systems, spin-phonon coupling and coherence engineering, and embedding of molecular spins in films and matrices. Relative to the established NV-ensemble quantum-sensing playbook (DEER, nanoscale NMR, T1 relaxometry at pT/sqrt(Hz) ensemble sensitivity), this is arguably the most direct molecular analogue in the search: the target sensitivity and readout protocols are borrowed straight from NV ensembles, but the emitter is synthetic. Newer, smaller group; good fit for a postdoc who wants to own a direction rather than inherit one.

Department(s)/lab(s): Physics – QOLS / Centre for Cold Matter | Ion Trapping Group (Thompson) @ Imperial
Summary:

Thompson leads the Ion Trapping Group at Imperial using RF (Paul) traps with laser-cooled Ca-40 ions and Penning traps. Research foci: (1) High-fidelity quantum logic gates — optimal control techniques for single-ion state manipulation and two-qubit gates; demonstrated >1 s coherence times via Ramsey interferometry in a Penning trap; (2) Precision spectroscopy — ytterbium ion optical clock uncertainty characterisation at 2.2×10^−18 fractional uncertainty (NPL collaboration); proposed precision laser spectrometer for highly charged ions (HCI) in cylindrical Penning traps for QED tests; (3) Axion sensing — collaborating with Devlin on the Penning-trap single-electron photon counter for axion searches; (4) Coulomb crystals — ultrahigh resolution spectroscopy of ion crystals. Past work includes SPECTRAP project at GSI Darmstadt for HCI spectroscopy.

Department(s)/lab(s): Institute of Physical Chemistry | van Slageren Group - Molecular Quantum Spintronics @ Stuttgart
Summary:

van Slageren's group is one of the leading molecular-qubit labs. They synthesize their own paramagnetic molecules, characterize them with a wide spectroscopic and magnetometric arsenal (multi-frequency and high-field EPR, pulsed EPR/DEER, THz spectroscopy, SQUID magnetometry) and back it with ab-initio calculation. Landmarks include room-temperature quantum coherence in a copper(II) molecular qubit, quantitative prediction of nuclear-spin-diffusion-limited coherence times, measurement of coherence in thin films without post-processing, and recent observation of a sizeable spin-electric effect -- electric-field control of a molecular spin state, which is the mechanism you would exploit for a molecular electrometer. Current direction: molecular quantum spintronics, marrying organic spintronics to molecular magnetism. Relative to the established NV-ensemble quantum-sensing playbook (DEER, nanoscale NMR, T1 relaxometry at pT/sqrt(Hz) ensemble sensitivity), this is the molecular alternative to the diamond defect: chemically tunable spin qubits whose coherence can be engineered by ligand design rather than by host-crystal purification. Immediate neighbours are Krueger (nanodiamond chemistry) and Wrachtrup (NV readout), both already on file -- an unusually complete local ecosystem.

Department(s)/lab(s): Chemistry – Photon Science Institute | Winpenny Group (Molecular Magnetism) @ Manchester
Summary:

Winpenny holds the Regius Chair in Chemistry at Manchester and is a world leader in molecular magnetism and molecular nanomagnets for quantum technologies. Research directions: (1) Molecular nanomagnets — synthesis of Cr7Ni 'horseshoe' rings and related cage clusters as prototype molecular qubits with long T2 times; (2) Multi-qubit molecular architectures — covalently linked molecular qubit pairs and arrays for quantum gate operations and distributed sensing; (3) Quantum error correction in molecules — designing molecular systems encoding logical qubits with error protection; (4) Quantum sensing applications — molecular spin systems as ultra-sensitive nanoscale magnetic sensors in the sub-nm regime. Leading the NPL M4Q Network and UK molecular qubit community.