Spin-Wave Multiplexed Atom-Cavity Electrodynamics

Abstract

We introduce multiplexed atom-cavity quantum electrodynamics with an atomic ensemble coupled to a single optical cavity mode. Multiple Raman dressing beams establish cavity-coupled spinwave excitations with distinctive spatial profiles. Experimentally, we demonstrate the concept by observing spin-wave vacuum Rabi splittings, selective superradiance, and interference in the cavitymediated interactions of two spin waves. We highlight that the current experimental configuration allows rapid, interchangeable cavity-coupling to 4 profiles with an overlap parameter of less than 10%, enough to demonstrate, for example, a quantum repeater network simulation in the cavity. With further improvements to the optical multiplexing setup, we infer the ability to access more than 10 3 independent spin-wave profiles.Significant resources are now being devoted to develop intermediate scale quantum systems with tens or hundreds of quantum bits, tunable interactions, and independent control of each element. Ion traps [1], superconducting circuits [2], tweezer arrays of neutral atoms [3], and other systems have made exciting recent advances, but scaling precise quantum dynamics from few-body to many-body remains as a primary challenge in quantum science.Instead of building up qubit-by-qubit, like the aforementioned platforms, here we focus on a system where quantum information is stored as patterns or images inside a single cavity-coupled atomic ensemble containing up to 10 6 atoms. This scalability more closely resembles, for example, that of a neural network, where data is stored and manipulated as patterns and images rather than binary bits [4][5][6][7].In this Letter, we introduce an apparatus that allows creation of multiple spin-wave excitations with unique spatial profiles. The spin waves are all collectively enhanced to emit into a single TEM00 cavity mode, and cavity coupling of each spin wave is dynamically controlled using a corresponding Raman dressing beam, generated by a two-dimensional acousto-optic deflector. Experimentally, we first observe strong spin wave/cavity interactions by measuring a dressed-state vacuum Rabi splitting (VRS) associated with the spin-wave Raman transition. Second, we discuss how spin waves are protected from cross-talk through collective dephasing, and demonstrate a high degree of distinguishability by observing selective superradiance over the continuum of spin-wave profiles. Finally, we observe interference as two spin-waves simultaneously interact with the cavity mode.As a multiplexed atom-cavity interface [8], our system may form the building block of a scalable quantum repeater [9]. Alternatively, this approach opens an elegant avenue to demonstrate a local bosonic quantum network for efficiently simulating many-body physics [10-12], generating samples from exponentially complex wave functions, or performing entanglement-enhanced or error-corrected quantum sensing. In the future, our multiplexed atom-cavity system may be combined with nonlinear cavity-mediated interactions or quantum nond...

Multicell Atomic Quantum Memory as a Hardware-Efficient Quantum Repeater Node

“…Currently in our experiment, the memory lifetime is limited by the atomic free expansion, which can be mitigated by loading the micro-ensembles into a dipole trap array [38]. Our setup can also be integrated with an optical cavity to increase the retrieval efficiency [29,39]. Toward a practical quantum repeater node, one can use telecom photons [40,41] for lower transmission loss at long distance.…”

Linear and continuous variable spin-wave processing using a cavity-coupled atomic ensemble

“…Overall, deterministic continuous-variable quantum computing has significantly better prospects for scalability than linear optics with single-quanta excitations, because the linear optics scheme requires a significant resource overhead to achieve deterministic processing [21]. However, in the near term, small-scale linear optical processing inside of a multiplexed quantum memory may be a significant boon toward realizing a quantum repeater with medium to high speed of entanglement generation over long distances (over 100 km) [8,45]. Meanwhile, in the continuous-variable scheme, the creation of spin-wave entangled states and the study of their uses for quantum sensing and networking applications should be one of the first experimental goals.…”

“…Recent experiments have introduced a path to use collective spin-wave excitations, holographically multiplexed, to achieve high-capacity quantum memories [6][7][8][9][10], but these experiments have not introduced a method to achieve full linear controllability of spin-wave excitations, a prerequisite for a universal quantum processor. Spin-wave quantum systems are being realized in multiple physical platforms including atomic vapors [7][8][9][10], solid-state crystals [11][12][13], and superconducting circuits [14]. Proposals for spin-wave readout of atomic arrays have also been developed [15][16][17].…”

Spin-Wave Quantum Computing with Atoms in a Single-Mode Cavity

“…This Letter builds upon a significant body of recent work in many-body cavity quantum electrodynamics [10][11][12][13][14][15][16][17] and memory experiments showing that quantum information can be stored as holographic spin waves in a large group of qubits [3,4,6,[18][19][20] that can be transferred to a readout bus for retrieval [8,[21][22][23]. Related work has theoretically investigated quantum information processing with holographic spin waves in superconducting circuits [3].…”

“…Related work has theoretically investigated quantum information processing with holographic spin waves in superconducting circuits [3]. Holographic quantum information is continuous, amenable to powerful and efficient quantum error correction [24], and can have collectively-enhanced qubit-light coupling [18]. However, no proposals have presented a method for efficient, universal quantum computation, because collective atomic ensembles have negligible atom-atom interactions, which are typically used for gate operations.…”