TY - JOUR
AU - Alec Cao
AU - William Eckner
AU - Theodor Yelin
AU - Aaron Young
AU - Sven Jandura
AU - Lingfeng Yan
AU - Kyungtae Kim
AU - Guido Pupillo
AU - Jun Ye
AU - Nelson Oppong
AU - Adam Kaufman
AB - Many-particle entanglement is a key resource for achieving the fundamental precision limits of a quantum sensor1. Optical atomic clocks2, the current state of the art in frequency precision, are a rapidly emerging area of focus for entanglement-enhanced metrology3–6. Augmenting tweezer-based clocks featuring microscopic control and detection7–10 with the high-fidelity entangling gates developed for atom-array information processing11,12 offers a promising route towards making use of highly entangled quantum states for improved optical clocks. Here we develop and use a family of multi-qubit Rydberg gates to generate Schrödinger cat states of the Greenberger–Horne–Zeilinger (GHZ) type with up to nine optical clock qubits in a programmable atom array. In an atom-laser comparison at sufficiently short dark times, we demonstrate a fractional frequency instability below the standard quantum limit (SQL) using GHZ states of up to four qubits. However, because of their reduced dynamic range, GHZ states of a single size fail to improve the achievable clock precision at the optimal dark time compared with unentangled atoms13. Towards overcoming this hurdle, we simultaneously prepare a cascade of varying-size GHZ states to perform unambiguous phase estimation over an extended interval14–17. These results demonstrate key building blocks for approaching Heisenberg-limited scaling of optical atomic clock precision.
BT - Nature
DA - 2024-10
DO - 10.1038/s41586-024-07913-z
IS - 8033
N2 - Many-particle entanglement is a key resource for achieving the fundamental precision limits of a quantum sensor1. Optical atomic clocks2, the current state of the art in frequency precision, are a rapidly emerging area of focus for entanglement-enhanced metrology3–6. Augmenting tweezer-based clocks featuring microscopic control and detection7–10 with the high-fidelity entangling gates developed for atom-array information processing11,12 offers a promising route towards making use of highly entangled quantum states for improved optical clocks. Here we develop and use a family of multi-qubit Rydberg gates to generate Schrödinger cat states of the Greenberger–Horne–Zeilinger (GHZ) type with up to nine optical clock qubits in a programmable atom array. In an atom-laser comparison at sufficiently short dark times, we demonstrate a fractional frequency instability below the standard quantum limit (SQL) using GHZ states of up to four qubits. However, because of their reduced dynamic range, GHZ states of a single size fail to improve the achievable clock precision at the optimal dark time compared with unentangled atoms13. Towards overcoming this hurdle, we simultaneously prepare a cascade of varying-size GHZ states to perform unambiguous phase estimation over an extended interval14–17. These results demonstrate key building blocks for approaching Heisenberg-limited scaling of optical atomic clock precision.
PY - 2024
SN - 1476-4687
SP - 315
EP - 320
T2 - Nature
TI - Multi-qubit gates and Schrödinger cat states in an optical clock
UR - https://doi.org/10.1038/s41586-024-07913-z
VL - 634
ER -