Next Generation Quantum Sensors
Engineering optically addressable molecular qubit sensors
Fluorescent proteins are the workhorses of in vivo bioimaging because they are water-soluble, genetically encodable, and low in toxicity. However, they have not previously been investigated as qubits. We recently realized a genetically encodable spin qubit encoded in enhanced Yellow Fluorescent Proteins that can be optically initialized, coherently driven with microwaves, and read out with up to 44% contrast. We further showed coherence times reaching 16 μs and magnetic field sensitivities 190 fT mol1/2 Hz−1/2. Finally, we showed that our qubits operate when expressed in living cells. Next, we aim to boost readout toward single-shot, extend measurement times by reducing photobleaching, and enhance optical and coherence properties via directed evolution and isotope engineering.
Publications:
- J. S. Feder, B. S. Soloway, S. Verma, Z. Z. Geng, S. Wang, B. Kifle, E. G. Riendeau, Y. Tsaturyan, L. R. Weiss, M. Xie, J. Huang, A. Esser-Kahn, L. Gagliardi, D. D. Awschalom, P. C. Maurer, A fluorescent-protein spin qubit, Nature 645, 73–79 (2025). [PDF]
Interfacing intact biomolecules with coherent diamond quantum sensors
Nitrogen-vacancy (NV) centers are powerful quantum sensors, but interfacing them with biomolecules has been a major obstacle to applications in the life sciences. Our lab developed a biocompatible surface architecture that allows us to anchor target biomolecules while preserving near-surface NV coherence. Using this platform, we created reproducible, spatially multiplexed DNA microarrays on diamond, verified sequence-specific hybridization, and detected binding events through NV sensing. Furthermore, careful passivation also allowed us to suppress surface paramagnetic “dark spins” below our detection limit. Next, we will translate our multiplexed sensor assays to medical diagnostics and minimally invasive surgery.
Collaborators: Aaron Esser-Kahn (UChicago), Alex High (UChicago), Giulia Galli (UChicago), Michael Flatté (Univ. of Iowa), and Joe Heremans (ANL)
Publications:
- I. Chi-Duran, E. J. Villafranca, D. Dang, R. Rosiles, C. T. Cheung, Z. Zhang, J. P. Cleveland, P. C. Maurer, Quantum biosensing on a multiplexed functionalized diamond microarray, arXiv:2508.13193 (2025). [PDF]
- Xie M, Yu X, Rodgers LVH, Xu D, Chi-Durán I, Toros A, Quack N, Leon NP de, Maurer PC (2022) Biocompatible surface functionalization architecture for a diamond quantum sensor. PNAS, 119(8) [PDF]
- Yu X, Villafranca EJ, Wang S, Jones JC, Xie M, Nagura J, Chi-Durán I, Delegan N, Martinson ABF, Flatté ME, Candido DR, Galli G, Maurer PC (2025) Engineering dark spin-free Diamond interfaces. arXiv.2504.08883 [PDF]
- Guo X, Xie M, Addhya A, Linder A, Zvi U, Wang S, Yu X, Deshmukh TD, Liu Y, Hammock IN, Li Z, DeVault CT, Butcher A, Esser-Kahn AP, Awschalom DD, Delegan N, Maurer PC, Heremans FJ, High AA (2024) Direct-bonded diamond membranes for heterogeneous quantum and electronic technologies. Nature comm., 15(1):8788 [PDF]
- Rodgers LVH, Hughes LB, Xie M, Maurer PC, Kolkowitz S, Bleszynski Jayich AC, Leon NP de (2021) Materials challenges for quantum technologies based on color centers in diamond. MRS bulletin, 46(7):623–633 [PDF]
Preparation of metrological states in dipolar-interacting spin systems
Improving sensitivity is central to nanoscale quantum sensing. While independent measurements of N identical qubits improve precision as 1/√N, entanglement can, in principle, reach the Heisenberg limit with 1/N scaling. Realizing such states robustly in solid-state spins has been elusive. We developed a variational control protocol that drives dipolar-coupled spin ensembles into metrologically useful entangled states without requiring knowledge of their spatial arrangement. The method uses only global single-qubit rotations and free dipolar evolution, which are experimentally accessible; depending on circuit depth and readout noise, our approach results in GHZ-like or spin-squeezed states. The approach is resilient to realistic imperfections, including initialization and readout errors, as well as dephasing.
Collaborators: Liang Jiang (UChicago), Aashish Clerk (UChicago), Fred Chong (UChicago), and Tian Zhong (UChicago)
Publications:
- Zheng T-X, Li A, Rosen J, Zhou S, Koppenhöfer M, Ma Z, Chong FT, Clerk AA, Jiang L, Maurer PC (2022) Preparation of metrological states in dipolar-interacting spin systems. npj quantum information, 8(1):1–7 [PDF]
- Zang A, Zheng T-X, Maurer PC, Chong FT, Suchara M, Zhong T (2025) Enhancing noisy quantum sensing by GHZ state partitioning. arXiv.2507.02829 [PDF]
- Ma Z, Gokhale P, Zheng T-X, Zhou S, Yu X, Jiang L, Maurer P, Chong FT (2021) Adaptive Circuit Learning for Quantum Metrology. 2021 IEEE Int. Conf. on Quant. Comp. and Eng. (QCE):419–430 [PDF]
Probing cellular processes with engineered diamond nanoprobes
Bulk diamond sensors are exceptionally sensitive but rely on macroscopic chiplets, limiting applications to in vitro measurements. Nanodiamonds, on the other hand, can enter living cells and have successfully been used for nanoscale thermometry. Although sensitive, recent experiments probing thermogenesis on a single-cell level have yielded drastically different results than would be expected based on simple thermodynamic calculations. We traced these discrepancies to surface noise that interferes with quantum measurements. In the process of investigating the cause, we developed engineered core-shell particles that are robust to this type of surface noise. Finally, by understanding the origin of this surface noise, we show that we can utilize nanodiamonds as a proxy to probe cellular activities reliably.
Collaborators: Nathalie de Leon (Princeton Univ.), Niels Quack (Univ. of Sydney), and Jason Cleveland (QDTI)
Publications:
- Zvi U, Mundhra S, Ovetsky D, Chen Q, Jones AR, Wang S, Roman M, Ferro M, Odunsi K, Garassino MC, Flatte ME, Swartz M, Candido DR, Esser-Kahn A, Maurer PC (2025) Probing cellular activity via charge-sensitive quantum nanoprobes. arXiv.2503.20816 [PDF]
- Zvi U, Candido DR, Weiss AM, Jones AR, Chen L, Golovina I, Yu X, Wang S, Talapin DV, Flatté ME, Esser-Kahn AP, Maurer PC (2025) Engineering spin coherence in core-shell diamond nanocrystals. Proceedings of the PNAS, 122(21):e2422542122 [PDF]
- Choi J, Zhou H, Landig R, Wu H-Y, Yu X, Von Stetina SE, Kucsko G, Mango SE, Needleman DJ, Samuel ADT, Maurer PC, Park H, Lukin MD (2020) Probing and manipulating embryogenesis via nanoscale thermometry and temperature control. PNAS, 117(26):14636–14641 [PDF]
Quantum sensing enabled μ-NMR spectroscopy with ppb resolution
Quantum sensing has enabled nanoscale and microscope NMR with exceptional sensitivity, but spectral resolution has been constrained by operating at magnetic fields below 1 T. However, since NMR resolution scales with field, high-resolution experiments require fields exceeding 14 T. Reaching this high-resolution regime requires new sensing sequences, terahertz-compatible engineering, and careful device integration. Over the past years, we have built an NV-enabled 14.1 T NMR platform targeting femtoliter-scale spectroscopy with parts-per-billion resolution, sufficient to extract detailed structural information from biologically relevant molecules.
Collaborators: Alex High (UChicago) and Joe Sachleben (UChicago – NMR facilities)