Mode multiplexing for scalable cavity-enhanced operations in neutral-atom arrays

TL;DR

The paper tackles the bottleneck of photon collection in large neutral-atom arrays by introducing cavity-mode multiplexing (CMM), which couples each atom to a distinct cavity mode in a single multimode cavity via controlled light shifts. This enables parallel, cavity-enhanced operations for fast non-destructive readout and high-rate remote entanglement, potentially yielding roughly two orders of magnitude speedup over free-space approaches. The authors present two concrete designs: one for rapid mid-circuit syndrome extraction across thousands of qubits and another for fast, heralded remote entanglement and teleported CNOTs between modules, with realistic numbers showing tens of microseconds cycle times and multi-MHz entanglement rates. Together, these results establish CMM as a scalable interface strategy that preserves compatibility with neutral-atom architectures while enabling modular, fault-tolerant quantum networks.

Abstract

Neutral atom arrays provide a versatile platform for quantum information processing. However, in large-scale arrays, efficient photon collection remains a bottleneck for key tasks such as fast, non-destructive qubit readout and remote entanglement distribution. We propose a cavity-based approach that enables fast, parallel operations over many atoms using multiple modes of a single optical cavity. By selectively shifting the relevant atomic transitions, each atom can be coupled to a distinct cavity mode, allowing independent simultaneous processing. We present practical system designs that support cavity-mode multiplexing with up to 50 modes, enabling rapid mid-circuit syndrome extraction and significantly enhancing entanglement distribution rates between remote atom arrays. This approach offers a scalable solution to core challenges in neutral atom arrays, advancing the development of practical quantum technologies.

Figures (5)

• Figure 1: Conceptual depiction of CMM in an atomic register. The bare cavity spectrum is shown on the left vertical axis, where distinct longitudinal and transverse modes appear at different frequencies. Site-selective control beams (blue) are used to induce light shifts on the excited state $\ket{e}$ via the $\ket{e}\!\rightarrow\!\ket{f}$ transition, thereby tuning the $\ket{g}\!\rightarrow\!\ket{e}$ transition frequency of each atom to match a different cavity resonance. External probe beams at the corresponding frequencies (red-orange-yellow) excite the atoms, and the emitted photons are coupled into their respective cavity modes. At the cavity output, the different modes are separated by a mode sorter for detection.
• Figure 2: Cavity and atom-array configuration for syndrome readout using CMM with $\mathrm{HG}_{n,0}$ modes. (a) Left: atom array with up to 6400 atoms, each coupled to a cavity mode. Right: atomic level scheme used for qubit readout. (b) Cavity spectrum showing the peak cooperativity of 25 equally-spaced $\mathrm{HG}$ modes spanning the FSR. Cooperativity values are normalized to $\eta_0$, the peak cooperativity of the $\mathrm{HG}_{0,0}$ mode. (c) Top: Spatial profiles of $\mathrm{HG}_{n,0}$ modes with indices $n=0,4,7$. Bottom: Cooperativity per atom across the array (every 8th atom shown). The color bar indicates cooperativity in both the mode profiles and the atom array map. Columns of atoms are placed at the intensity maxima of the $\mathrm{HG}_{n,0}$ modes as indicated by the dashed circles, with odd (even) values of $n$ assigned to the positive (negative) $x$-axis. Each column is divided into two registers, which couple to two longitudinal cavity modes with the same transverse profile, separated in frequency by one FSR.
• Figure 3: Scaling of syndrome readout duration using free-space imaging (orange), a single cavity mode (grey), and CMM over 50 cavity modes (blue), assuming $p_{\mathrm{synd}}\!=\!5 \!\times\!10^{-3}$ and $10µ s$ query time. Compared to free-space readout, CMM offers a speed-up of two orders of magnitude, allowing readout of $5000$ syndrome qubits within $50µ s$.
• Figure 4: Cavity and atom-array configuration for remote atom–atom Bell-state generation using CMM with radial $\mathrm{LG}_{p,0}$ modes.(a) Left: 1D array with up to 255 atoms, where each atom is coupled to one of the cavity modes. Groups of consecutive atoms form registers, each associated with a distinct cavity mode. A control beam scans across the array, sequentially coupling atoms in each register to their assigned mode. Right: atomic level scheme for atom–photon entanglement via vSTIRAP. (b) Cavity spectrum showing the peak cooperativity of 33 equally-spaced LG modes across the FSR, given relative to the peak cooperativity of the $\mathrm{LG}_{0,0}$ mode, denoted $\eta_0$. The peak cooperativity remains unchanged for the higher-order radial LG modes. (c) Spatial profiles of $\mathrm{LG}_{p,0}$ modes with indices $p = 0, 2, 4, 8$. (d) Cooperativity reduction of each mode as a function of temperature.
• Figure 5: Photon generation using vSTIRAP. Simulated photon flux at the cavity output (blue) produced by a linearly increasing external probe field (orange) as a function of time. The simulation assumes $\eta\!=\!7$ and the cavity parameters described in the main text. The solid and dotted lines correspond to two different slopes of the external probe, resulting in distinct photon temporal profiles, with the solid line representing the probe drive chosen for our application. The dotted probe drive saturates the vSTIRAP adiabaticity condition, resulting in the photon generation probability given by Eq. \ref{['eq:alpha_interface']}, but at the cost of a reduced generation rate.