Technique - (10) Trapped-ion quantum logic spectroscopy

Type: Experimental

Description: Using quantum logic techniques with two-species ion chains (e.g., Be+/Ca+ or Ba+) for high-precision spectroscopy and quantum state readout of complex ions.

Department(s)/lab(s): Physics – Institute for Quantum Electronics | Quantum Control for Fundamental Physics Group (Craik Group) @ ETH Zurich
Summary:

Craik leads the RAVIOLIS project (SNSF Starting Grant, started July 2025) measuring atomic parity violation in barium ions at <0.1% precision. Her entanglement protocol uses multi-ion entangled states with photonic integrated waveguide addressing to common-mode-reject parity-conserving systematics. Previous work: precision measurement of Ba+ dipole transition probabilities below 1% uncertainty; first laser-guided individual addressing of Ba+ qubits with <10^-4 intensity crosstalk; isotope-shift spectroscopy in Ca+ for fifth-force searches. She is actively recruiting for postdocs and PhD students for the new Ba+ ion trap experiment.

Department(s)/lab(s): Physics (Clarendon Laboratory) | Ion Trap Quantum Computing Group @ Oxford
Summary:

Ballance develops techniques and technologies (including cryogenic ion traps and integrated photonic addressing chips) to control trapped atomic-ion qubits with high fidelity at scale, co-founding the spin-out company Oxford Ionics to commercialise the approach.

Department(s)/lab(s): School of Physics | Berengut Atomic Structure and Clocks Theory Group @ UNSW
Summary:

Berengut works on the atomic structure theory underpinning next-generation clocks: highly charged ions, whose optical transitions are both extremely narrow and exceptionally sensitive to variation of fundamental constants and to new physics, and the thorium-229 nuclear clock. He identifies which ionic species and transitions maximise sensitivity to the physics of interest while remaining experimentally accessible, and computes the many-body structure needed to interpret them — work that has directly guided the experimental HCI clock programmes at PTB, MPIK and NIST. 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 — clocks and magnetometers are the two great classes of quantum sensor; his work is on the frequency side of the same estimation problem that fixes pT/sqrt(Hz) performance on the magnetic side. Theory PI with close experimental collaborations.

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

Biercuk's Quantum Control Laboratory sits precisely at the intersection of control engineering and precision measurement. The group uses trapped ytterbium ions — including large 2D Penning-trap crystals — as both quantum simulators and as calibrated sensors, and is best known for noise spectroscopy: using the qubit itself as a spectrum analyser of its environment, then designing dynamical-decoupling and open-loop control sequences that null the dominant noise. That programme produced Q-CTRL, his quantum control software company, and more recently a serious push into quantum sensing for navigation (magnetic anomaly navigation, quantum-enhanced RF sensing) as a commercial and defence application. 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 filter-function and noise-spectroscopy formalism is now standard equipment in the NV community for designing the DEER and dynamical-decoupling sequences that deliver pT/sqrt(Hz) sensitivity; a candidate from that background would find the theoretical toolkit immediately familiar. Large, well-funded group with strong industry pathways.

Department(s)/lab(s): Physics | Fan Group @ Harvard
Summary:

Fan is a junior faculty member specializing in searches for physics beyond the Standard Model through precision measurements using ion traps and molecules. Included as a borderline quantum-sensing/precision-measurement case, analogous to eEDM-style molecular and ion-trap metrology elsewhere in the department.

Department(s)/lab(s): Physics | Haeffner Ion Trap Lab @ UCB
Summary:

Haeffner's group traps and coherently controls individual and few-ion crystals to perform quantum logic spectroscopy, entanglement-enhanced metrology, and quantum simulation, using trapped ions as some of the most precisely controllable quantum sensors available. The lab is actively recruiting postdocs to work on next-generation ion-trap sensing and control techniques.

Department(s)/lab(s): Physics – Institute for Quantum Electronics | Trapped Ion Quantum Information Group (Home Group) @ ETH Zurich
Summary:

Home leads the TIQI group working with Be+ and Ca+ trapped ions. Research directions: (1) Quantum error correction — fault-tolerant gates, surface code implementations with multi-ion chains; (2) Precision metrology — ytterbium ion optical clock, mixed-species ion chain spectroscopy and ytterbium HFS measurements; (3) Macroscopic superposition and quantum contextuality — creating nonclassical motional states in harmonic oscillators for tests of quantum foundations; (4) Scalable architectures — photonic integrated waveguides for individual ion addressing, quantum logic detection of spectroscopy ions. Key publications include first two-qubit gates with mixed species and records in quantum state readout fidelity. Lab is investigating quantum logic-enhanced spectroscopy of complex atomic systems.

Department(s)/lab(s): Physics & Astronomy | Schuessler Laser Spectroscopy & Ion Trap Group @ TAMU
Summary:

Schuessler combines optical frequency combs with cavity-enhanced and mid-IR spectroscopy for ultrasensitive trace-gas and isotopic detection, and runs ion-trap precision mass/laser spectroscopy of exotic species. In the broader landscape of NV-centre ensemble quantum sensing (DEER, nano-NMR, T1 relaxometry) operating near pT/sqrt(Hz) sensitivity, this work is a comb-metrology counterpart to spin-based chemical sensing.

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

Tan trained at NIST Boulder in the Wineland lineage and brought quantum-logic spectroscopy and entanglement-enhanced metrology to Sydney. His independent programme builds trapped-ion systems for quantum simulation of vibronic and chemical dynamics, for bosonic/qudit encodings, and — most relevant here — for precision measurement that exploits entangled states to beat the standard quantum limit. The group also works on high-fidelity gates and on using motional modes as sensitive transducers of weak forces and electric fields. 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 — entanglement-enhanced protocols are the natural next step beyond the shot-noise-limited pT/sqrt(Hz) ensemble measurements that define the current NV state of the art, and Tan is one of a small number of Australian PIs actually implementing them. Mid-career, actively building; a strong option for a candidate wanting to move from spin ensembles to entangled sensors.

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

Wolf works on trapped-ion quantum sensing, using the motional degrees of freedom of single ions and small crystals as transducers for weak electric fields and forces, together with non-classical motional states (squeezed and Fock states) to enhance the achievable sensitivity. The broader agenda is to use trapped ions as a testbed for fundamental measurement limits — quantum-enhanced amplification of small displacements, quantum non-demolition readout of motion — with an eye to applications in electric-field metrology and searches for new physics. 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 — trapped-ion motional sensing is the cleanest available platform for demonstrating the entanglement-enhanced scaling that NV ensembles at pT/sqrt(Hz) approach only in the shot-noise-limited regime. Early-career independent PI within the Quantum Control Laboratory; smaller group, higher autonomy.