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arXiv:2601.08921

Simultaneous nondestructive measurement of many polar molecules using Rydberg atoms

Jeremy T. Young, Kang-Kuen Ni, Alexey V. Gorshkov

quant-phphysics.atom-phSubmitted Jan 13, 2026• Announced Jan 15, 2026• 0 citations
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Abstract

Tweezer arrays of polar molecules present new opportunities for quantum science and quantum information. However, a major challenge, especially in bialkali molecule platforms, is the fact that current measurement schemes for the internal states are destructive. In this work, we present a method to use Rydberg atoms to nondestructively measure the internal state of a molecular qubit. We achieve this via microwave dressing of both molecules and Rydberg atoms, allowing us to tune the interactions so that there are minimal Rydberg-Rydberg interactions and many measurements can take place simultaneously. We consider two experimentally-motivated examples of detecting $^{23}$Na$^{133}$Cs and $^{87}$Rb$^{133}$Cs with $^{133}$Cs atoms. Finally, we discuss several strategies for mitigating various sources of crosstalk.

Comments
5 + 2 pages, 4 + 1 figures

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Tweezer arrays of polar molecules present new opportunities for quantum science and quantum information. However, a major challenge, especially in bialkali molecule platforms, is the fact that current measurement schemes for the internal states are destructive. In this work, we present a method to use Rydberg atoms to nondestructively measure the internal state of a molecular qubit. We achieve this via microwave dressing of both molecules and Rydberg atoms, allowing us to tune the interactions so that there are minimal Rydberg-Rydberg interactions and many measurements can take place simultaneously. We consider two experimentally-motivated examples of detecting 23^{23}23Na133^{133}133Cs and 87^{87}87Rb133^{133}133Cs with 133^{133}133Cs atoms. Finally, we discuss several strategies for mitigating various sources of crosstalk.
We propose a scheme for mediating many simultaneous, fast entangling gates between pairs of polar molecules using Rydberg atoms. By using microwave drives, the dipolar interactions between Rydberg atoms are nullified. Using the freedom left in the microwave dressing parameters, the Rydberg van der Waals interactions are minimized and the Rydberg-molecule interaction is tuned into resonance, allowing for the mediation of a modified iSWAP gate between molecules. In the example of mediating gates between 23Na133Cs\rm{{}^{23}Na {}^{133}Cs}23Na133Cs molecules with 133Cs\rm {}^{133}Cs133Cs atoms, the gate is more than two orders of magnitude faster than an equivalent direct molecule-molecule gate. We model the decay of the dressed Rydberg states and the motion of the atom and molecules and obtain a leading-order estimate of the resulting gate infidelities. Finally, we show that by detecting the state of the Rydberg atom after a gate, a subset of gate errors can be converted into erasure errors and mitigated by post-selection or quantum error-correction.
We analyze the possibility to exploit charge-dipole interaction between a single polar molecule or a one-dimensional (1D) molecular array and a single Rydberg atom to read out molecular rotational populations. We calculate the energy shift of a single Rb(60s\mathrm{Rb}(60sRb(60s) atom interacting with a single KRb or RbYb molecule in their lowest two rotational states. At atom-molecule distances, relevant to trapping of molecules in optical lattices, the Rydberg electron energy shifts conditioned on the rotational states, are of the order of several MHz. Atom excitation to a Rydberg state and detection of atomic fluorescence conditioned on a rotational state preserves the molecule, making our scheme a nondestructive measurement of the rotational state. Similarly, a 1D array of polar molecules can shift the electron energy of a blockaded Rydberg superatom. We consider a scheme to read out the molecular array collective rotational states using the conditioned Rydberg energy shifts, and numerically analyze a system with three and five KRb or RbYb molecules interacting with Rb(60s\mathrm{Rb}(60sRb(60s) superatom.
We present a new approach to investigating Rydberg molecules by demonstrating the formation and characterization of individual Rb^{*}Cs Rydberg molecules using optical tweezers. By employing single-atom detection of Rb and Cs, we observe molecule formation via correlated loss of both species and study the formation dynamics with single-particle resolution. We control the interatomic distances by manipulating the relative wave function of atom pairs using the tweezer intensity, optimizing the coupling to molecular states and exploring the effect of the tweezer on these states. Additionally, we demonstrate molecule association with atoms trapped in separate tweezers, paving the way for state-selective assembly of polyatomic molecules. The observed binding energies, molecular alignment, and bond lengths are in good agreement with theory. Our approach is broadly applicable to Rydberg tweezer platforms, expanding the range of available molecular systems and enabling the integration of Rydberg molecules into existing quantum science platforms.
The ability to locally control and measure subsets of ancilla qubits in an efficient and crosstalk-free manner is a key ingredient in quantum error correction (QEC). Dual-species neutral atom arrays offer an ideal implementation of these capabilities, enabling independent state preparation, manipulation, and detection on each species. In this work, we realize such a dual-species Rydberg array of Na and Cs atoms trapped in co-localized 2D optical tweezer arrays, using Na as an ancilla to measure stabilizers of surrounding Cs data qubits. We identify the finite interspecies Rydberg-Rydberg interaction strength as a practical obstacle to high-fidelity multi-body entanglement and show that, by tuning the Rabi frequency and the detuning of the Rydberg driving field, the resulting geometric phase error can be compensated. This yields a protocol for simultaneous, non-destructive, in situ stabilizer readout of multiple data qubits via global pulses alone. Using this protocol, we demonstrate non-destructive measurement of Pauli-Z stabilizers on four-qubit Cs plaquettes via a single global Rydberg pulse sequence. Our results demonstrate dual-species tweezer arrays as a promising route towards scalable QEC and open the door to new quantum control protocols leveraging both interspecies and intraspecies interactions.
A highly sensitive, general, and preferably nondestructive technique to detect polar molecules would greatly advance a number of fields, in particular quantum science with cold and ultracold molecules. Here, we propose using resonant energy transfer between molecules and Rydberg atoms to detect molecules. Based on an energy transfer cross-section of > 10 −6 cm 2 for sufficiently low collision energies, a near unit efficiency non-destructive detection of basically any polar molecule species in a well-defined internal state should be possible.
We study the possibility to use interaction between a polar molecule in the ground electronic and vibrational state and a Rydberg atom to construct two-qubit gates between molecular qubits and to coherently control molecular states. A polar molecule within the electron orbit in a Rydberg atom can either shift the Rydberg state, or form a Rydberg molecule. Both the atomic shift and the Rydberg molecule states depend on the initial internal state of the polar molecule, resulting in molecular state dependent van der Waals or dipole-dipole interaction between Rydberg atoms. Rydberg atoms mediated interaction between polar molecules can be enhanced up to 10(3) times. We describe how the coupling between a polar molecule and a Rydberg atom can be applied to coherently control molecular states, and specifically, to individually address molecules in an optical lattice, and to non-destructively readout molecular qubits.