Technique - (9) Pulsed EPR / DEER molecular qubit spectroscopy

Type: Experimental

Description: Multi-frequency pulsed electron paramagnetic resonance including dynamical decoupling, ENDOR, and DEER/PELDOR for measuring coherence and inter-qubit couplings in molecular spin systems.

Department(s)/lab(s): Chemistry | Anderson Lab @ UChicago
Summary:

Anderson's group designs molecular electron-spin qubit candidates -- including an air- and water-stable tetrathiafulvalene-bridged radical with spin centered on a nuclear-spin-free ligand -- that retain hundreds of nanoseconds of coherence in solution at room temperature, aiming toward solution-phase quantum sensing in biological environments. This complements solid-state NV-ensemble sensors, which use DEER, NMR, and T1-relaxometry protocols to reach pT/sqrt(Hz)-class magnetic sensitivity, by pursuing a chemically tunable molecular alternative that could operate directly in biological media.

Department(s)/lab(s): Physics (Condensed Matter Physics Sub-department) | Quantum Spin Dynamics Group @ Oxford
Summary:

Ardavan leads the Quantum Spin Dynamics group, studying quantum coherent phenomena in condensed matter. Central to the lab's quantum sensing relevance: (1) molecular spin qubits — using pulsed EPR/DEER to characterise and control multi-spin registers ({Cr7Ni} molecular rings, nitroxide radical chains) assembled into qubit networks, measuring coherence times, inter-qubit couplings, and demonstrating spin-electric coupling in molecular magnets; (2) DNA-assembled molecular quantum devices — using DNA nanostructures to precisely position molecular spin qubits for multi-qubit sensing and quantum information applications; (3) surface atom spin resonance — STM-based coherent spin control of individual atoms on surfaces at nanosecond timescales. Uses X-band through W-band pulsed EPR at Centre for Advanced Electron Spin Resonance (CAESR), Oxford.

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

Boskovic is a synthetic inorganic chemist working on lanthanoid and polyoxometalate molecular magnets, valence tautomeric and redox-switchable complexes, and the design of molecules whose spin states can be addressed and switched. The group's relevance to quantum sensing is that these are chemically tunable spin qubits: unlike solid-state defects, their coordination environment, nuclear-spin bath and anisotropy can be designed atom by atom, which is the argument for molecular qubits as sensors. Characterisation is by SQUID magnetometry, EPR and ab initio calculation. 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 — molecular spin qubits are the chemistry community's answer to the NV centre, and DEER/pulsed-EPR protocols developed for NV ensembles at pT/sqrt(Hz) transfer more or less directly to these systems. Borderline inclusion (synthesis-led rather than sensitivity-led), kept per the inclusive rubric.

Department(s)/lab(s): Chemistry – Photon Science Institute / National EPR Facility | Bowen Group (Molecular Spin Qubits and EPR) @ Manchester
Summary:

Bowen leads the CQSE 'Spins and Qubits' theme at Manchester, focusing on organometallic molecular spin qubits for quantum sensing and computing. Research directions: (1) Organometallic La(II) and other rare-earth molecular qudits — designing molecules with multiple accessible spin states (qudits) for encoding quantum information and sensing; (2) Pulsed EPR characterization — Hahn echo, ESEEM, ENDOR at X/W/Q-band to measure coherence times and hyperfine couplings; (3) Integration of molecular qubits into devices — surface deposition and nanoscale addressing; (4) Multi-spin sensing — using exchange-coupled spin pairs as differential sensors of magnetic field gradients. Closely collaborates with Tuna and Winpenny.

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 — DEER, nanoscale NMR and T1 relaxometry protocols operating at pT/sqrt(Hz) field sensitivity — 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): 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 — pulsed EPR, ODMR, dynamical decoupling, relaxometry — 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 — DEER, nanoscale NMR and T1 relaxometry protocols operating at pT/sqrt(Hz) field sensitivity — 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 — 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 – 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 — Hahn echo, ESEEM, ENDOR, DEER for structural and electronic characterization of inorganic and organometallic complexes; (2) Molecular spin qubits — [Cu(mnt)2]²⁻ and related molecules as candidate qubits; measuring coherence times and investigating decoherence mechanisms; (3) Multi-qubit molecular registers — using exchange interactions for two-qubit gates within a molecule; (4) Magnetic sensing applications — molecular systems for magnetic field sensing below the diffraction limit. Partner of NPL M4Q EPSRC Network for Materials for Quantum.

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): 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.