Collectively Encoded Rydberg Qubit

Abstract

We demonstrate a collectively-encoded qubit based on a single Rydberg excitation-a Rydberg polariton-stored in an ensemble of N entangled atoms. Qubit rotations are performed by applying microwave fields that drive excitations between Rydberg states. Coherent read-out is preformed by mapping the polariton into a single photon. Ramsey interferometry is used to probe the coherence of the qubit, and test the robustness to external perturbations. We show that the Ramsey fringe visibility is independent of atom loss, and that dephasing due to electric field noise scales as the forth power of field amplitude. These results show that robust quantum information processing can be achieved via collective encoding using Rydberg polaritons, and hence this system could provide attractive alternative coding strategies for quantum computation and networking.

An Intracavity Rydberg Superatom for Optical Quantum Engineering: Coherent Control, Single-Shot Detection and Optical $π$ Phase Shift

“…We show that the cloud acts as a single Rydberg superatom with a collectively enhanced coupling to light, which we can coherently manipulate and optically detect in a single shot with a 95% efficiency via the transmission of the cavity. Most importantly, with respect to recent experiments on Rydberg superatoms [25][26][27][28], we successfully unlocked a qualitatively new regime where the phase of the light reflected from the cavity is shifted by π by a single Rydberg excitation, allowing us to detect the latter with a 90% efficiency via a homodyne measurement. This π phase rotation, together with the coherent control and the single-shot state detection, is crucial for implementing two-photon quantum gates [29] and for generating non-classical optical resources for quantum sensing and communications.…”

Facilitation-Induced Transparency and Single-Photon Switch with Dual-Channel Rydberg Interactions

“…Cold gases of Rydberg atoms have emerged as a versatile platform for studying quantum nonlinear optics, nonequilibrium statistical physics, and quantum simulation of strongly interacting many-body systems [1][2][3][4], including antiferromagnetic phase transition [5,6], quantum many-body scars [7][8][9], and Heisenberg XYZ spin model [10]. At the same time, Rydberg atoms are of technological importance, which allow to create collectively encoded qubit [11,12], entanglement [13,14], photonic or neutral-atom gates for quantum information processing [1,[15][16][17], precision measurements [18,19], and so on. The enabled fundamental research and practical applications are rooted largely by the fact that Rydberg atoms offer strong and long-ranged interactions.…”

Proposal of ensemble qubits with two-atom decay

“…Despite such considerable developments, exploiting an ensemble as a single qubit remains a challenge, due to the requirement of a strong anharmonicity. Previous approaches, which have been proposed to encode an ensemble qubit, usually rely on Rydberg dipole blockade [18][19][20][21][22][23][24][25][26][27], and require strong dipole-dipole interactions between highly excited atoms. However, for typical ensembles, it is much easier to control atoms in the ground state manifold, and in this case atomatom interactions are extremely weak.…”