Quantum-enhanced sensing of displacements and electric fields with large trapped-ion crystals

Abstract

Developing the isolation and control of ultracold atomic systems to the level of single quanta has led to significant advances in quantum sensing, yet demonstrating a quantum advantage in real world applications by harnessing entanglement remains a core task. Here, we realize a many-body quantum-enhanced sensor to detect weak displacements and electric fields using a large crystal of ∼ 150 trapped ions. The center of mass vibrational mode of the crystal serves as high-Q mechanical oscillator and the collective electronic spin as the measurement device. By entangling the oscillator and the collective spin before the displacement is applied and by controlling the coherent dynamics via a many-body echo we are able to utilize the delicate spin-motion entanglement to map the displacement into a spin rotation such that we avoid quantum back-action and cancel detrimental thermal noise. We report quantum enhanced sensitivity to displacements of 8.8 ± 0.4 dB below the standard quantum limit and a sensitivity for measuring electric fields of 240 ± 10 nVm −1 in 1 second (240 nVm −1 / √ Hz).

Collective Spin-Light and Light-Mediated Spin-Spin Interactions in an Optical Cavity

“…the smaller the atom number, the more severely the finite size of the Bloch sphere limits the Wineland parameter. We note, however, that there are approaches beyond spin squeezing that are not limited by the curvature of the Bloch sphere [55,[111][112][113].…”

Tailored generation of quantum states in an entangled spinor interferometer to overcome detection noise

“…Retaining only terms to quadratic order, it is straightforward to obtain the minimum of the sensitivity as (∆ϕ) 2 √ 3)/2 in the limit of large n n s , 1. For completeness, we follow a similar recipe to obtain the results (34) and (36) where θ s or n s are allowed to randomly fluctuate due to imperfect state preparation.…”

“…As such a capability is technically demanding, even in state-of-the-art experiments, and dif-ficult to scale with particle number [28] there have been efforts to overcome this limitation by developing novel methods such as interaction-based readout (IBR) [29][30][31][32]. Despite notable demonstrations [21,33,34], IBR methods require a level of coherent control over the dynamics that can be demanding or impractical for many experimental platforms. Consequently, it is important to assess the metrological utility of quantum states with a practical viewpoint, striking a balance between idealized metrological enhancement and robustness to technical noise.…”

Phonon-laser ultrasensitive force sensor

“…With development of nanotechnology using atomic and molecular sensors, the physical quantities have been detected in a higher level of sensitivity than ever before due to the excellent perceived performance of the sensors [1][2][3][4][5][6][7][8]. Force detection has been always taking an important role in precision measurement since all the changes of motion are concerned with the force due to Newton's laws, where the small force detection by trapped ions or atoms has recently demonstrated the superiority of high sensitivity and broad adjustability [9][10][11][12][13][14][15][16]. The weak AC electric force was sensitively detected by means of spin-motion entanglement in two-dimensional trapped-ion mechanical oscillators [9][10][11].…”

“…Force detection has been always taking an important role in precision measurement since all the changes of motion are concerned with the force due to Newton's laws, where the small force detection by trapped ions or atoms has recently demonstrated the superiority of high sensitivity and broad adjustability [9][10][11][12][13][14][15][16]. The weak AC electric force was sensitively detected by means of spin-motion entanglement in two-dimensional trapped-ion mechanical oscillators [9][10][11]. The radio-frequency electric force as small as 5 yN was measured, based on the technique of injection-locked phonon laser, by observing the range of injected frequency and the gravity variance of the ion's displacement [12].…”