Curator's Take
AI Commentary
This article shows a practical way to amplify the state of a single atom by imprinting its phase onto an entire Rydberg‑dressed lattice, achieving non‑destructive readout with >99.8 % fidelity despite fluctuations in atom number. By making the per‑atom phase shift independent of ensemble size, the technique sidesteps two major hurdles—precise gate programming and loss‑sensitive coupling—that have limited similar hybrid qubit‑ensemble schemes. The result opens a clear path toward scalable quantum memories and error‑corrected registers that can reliably transfer information between microscopic processors and mesoscopic storage blocks. However, extending the method beyond eight atoms will require careful control of dressing fields and lattice homogeneity to preserve the number‑insensitive phase shift.
— Mark Eatherly
Summary
The amplification of quantum information carried by a single quantum excitation is a recurring challenge across diverse quantum platforms. The coupling between a single qubit and a mesoscopic ensemble of spins, for example, can be leveraged to realize non-destructive detection of the qubit state. However, realizing robust couplings between such systems is experimentally challenging and typically requires programmable quantum gates or native long-range interactions. Here, we introduce a platform that couples a single qubit, encoded in the ground-to-Rydberg transition of a control atom, to a Rydberg-dressed target ensemble of ground-state atoms trapped in an optical lattice. We show that the state of the control qubit can be coherently mapped onto the ensemble via a qubit-controlled collective phase shift. By Rydberg-dressing the ensemble, the controlled phase shift per target atom becomes independent of the number of target atoms, making the protocol intrinsically insensitive to atom-number fluctuations and atom loss, which are the dominant experimental imperfections in our system. Exploiting the collective response of up to eight target spins, we demonstrate the efficacy of the scheme by realizing non-destructive detection of a single Rydberg excitation with a state-assignment fidelity of $\mathcal{F} = 99.81^{+0.17}_{-1.47}\,\%$. Our approach demonstrates the key ingredients for high-fidelity transfer of quantum information from a single qubit to a mesoscopic ensemble, opening a route to non-destructive mid-circuit readout of Rydberg states and to efficient interfaces between single qubits and photonic modes.