新しいスピン・スクイーズ技術により、より優れた量子測定のために原子を協働させることが可能になる(New Spin-Squeezing Techniques Let Atoms Work Together for Better Quantum Measurements)

2023-09-25 米国国立標準技術研究所(NIST)

＜関連情報＞

• https://www.nist.gov/news-events/news/2023/09/new-spin-squeezing-techniques-let-atoms-work-together-better-quantum
• https://www.nature.com/articles/s41586-023-06472-z
• https://www.nature.com/articles/s41586-023-06360-6

有限距離相互作用による光遷移の量子計測 Quantum-enhanced sensing on optical transitions through finite-range interactions

Johannes Franke,Sean R. Muleady,Raphael Kaubruegger,Florian Kranzl,Rainer Blatt,Ana Maria Rey,Manoj K. Joshi & Christian F. Roos
Nature  Published:30 August 2023
DOI:https://doi.org/10.1038/s41586-023-06472-z

Abstract

The control over quantum states in atomic systems has led to the most precise optical atomic clocks so far^1,2,3. Their sensitivity is bounded at present by the standard quantum limit, a fundamental floor set by quantum mechanics for uncorrelated particles, which can—nevertheless—be overcome when operated with entangled particles. Yet demonstrating a quantum advantage in real-world sensors is extremely challenging. Here we illustrate a pathway for harnessing large-scale entanglement in an optical transition using 1D chains of up to 51 ions with interactions that decay as a power-law function of the ion separation. We show that our sensor can emulate many features of the one-axis-twisting (OAT) model, an iconic, fully connected model known to generate scalable squeezing⁴ and Greenberger–Horne–Zeilinger-like states^5,6,7,8. The collective nature of the state manifests itself in the preservation of the total transverse magnetization, the reduced growth of the structure factor, that is, spin-wave excitations (SWE), at finite momenta, the generation of spin squeezing comparable with OAT (a Wineland parameter^9,10 of −3.9 ± 0.3 dB for only N = 12 ions) and the development of non-Gaussian states in the form of multi-headed cat states in the Q-distribution. We demonstrate the metrological utility of the states in a Ramsey-type interferometer, in which we reduce the measurement uncertainty by −3.2 ± 0.5 dB below the standard quantum limit for N = 51 ions.

光クロックでリュードベリ相互作用によるスピンスクイーズを実現 Realizing spin squeezing with Rydberg interactions in an optical clock

William J. Eckner,Nelson Darkwah Oppong,Alec Cao,Aaron W. Young,William R. Milner,John M. Robinson,Jun Ye & Adam M. Kaufman
Nature  Published:30 August 2023
DOI:https://doi.org/10.1038/s41586-023-06360-6

Abstract

Neutral-atom arrays trapped in optical potentials are a powerful platform for studying quantum physics, combining precise single-particle control and detection with a range of tunable entangling interactions^1,2,3. For example, these capabilities have been leveraged for state-of-the-art frequency metrology^4,5 as well as microscopic studies of entangled many-particle states^{6,7,8,9,10,11}. Here we combine these applications to realize spin squeezing—a widely studied operation for producing metrologically useful entanglement—in an optical atomic clock based on a programmable array of interacting optical qubits. In this demonstration of Rydberg-mediated squeezing with a neutral-atom optical clock, we generate states that have almost four decibels of metrological gain. In addition, we perform a synchronous frequency comparison between independent squeezed states and observe a fractional-frequency stability of 1.087(1) × 10⁻¹⁵ at one-second averaging time, which is 1.94(1) decibels below the standard quantum limit and reaches a fractional precision at the 10⁻¹⁷ level during a half-hour measurement. We further leverage the programmable control afforded by optical tweezer arrays to apply local phase shifts to explore spin squeezing in measurements that operate beyond the relative coherence time with the optical local oscillator. The realization of this spin-squeezing protocol in a programmable atom-array clock will enable a wide range of quantum-information-inspired techniques for optimal phase estimation and Heisenberg-limited optical atomic clocks^{12,13,14,15,16}.