arXiv:1912.10550 · Physical Review Letters

Truncated Nonlinear Interferometry for Quantum-Enhanced Atomic Force Microscopy

Raphael C. Pooser, Nicholas J. Savino, Emma Batson, Jacob L. Beckey, Javier A. García, Benjamin J. Lawrie

Published Jun 12, 2020• 59 citations

Abstract

Nonlinear interferometers that replace beam splitters in Mach-Zehnder interferometers with nonlinear amplifiers for quantum-enhanced phase measurements have drawn increasing interest in recent years, but practical quantum sensors based on nonlinear interferometry remain an outstanding challenge. Here, we demonstrate the first practical application of nonlinear interferometry by measuring the displacement of an atomic force microscope microcantilever with quantum noise reduction of up to 3 dB below the standard quantum limit, corresponding to a quantum-enhanced measurement of beam displacement of 1.7 fm/sqrt[Hz]. Further, we minimize photon backaction noise while taking advantage of quantum noise reduction by transducing the cantilever displacement signal with a weak squeezed state while using dual homodyne detection with a higher power local oscillator. This approach may enable quantum-enhanced broadband, high-speed scanning probe microscopy.

DOI: 10.1103/physrevlett.124.230504

Related papers

Truncated nonlinear interferometer-based atomic force microscopes

Raphael C. Pooser

A truncated non-linear interferometer-based atomic force microscope (AFM) includes an input port and a non-linear amplifier that renders a probe beam and a conjugate beam. The AFM includes local oscillators having a relationship with the probe beam and the conjugate beam. The displacement of the AFM's cantilever is transduced by the probe beam, and/or the conjugate beam or their respective local oscillators. The AFM's phase-sensitive detectors detect a phase modulation between the respective local oscillators and the probe beam and the conjugate beam. The detected phase modulation corresponds to the change in phase. The AFM's circuitry measures phase signals that are indicative of the cantilever displacement. The resulting measurement signals exhibit a quantum noise reduction in either the intensity difference or phase sum quadrature.

Jan 23, 20230 citations

Truncated Nonlinear Interferometric Cantilever Beam-Displacement: Accessible Quantum Sensing

Benjamin J. Lawrie, Jacob L. Beckey, Raphael C. Pooser

We show that relative beam displacement measurements with two-mode squeezed light sources are identical to truncated SU(1,1) interferometers, enabling a new quantum-enhanced atomic force microscopy suitable for broadband characterization of high-speed dynamics in materials.

Conference on Lasers and Electro-OpticsMay 5, 20190 citations

Truncated nonlinear interferometric cantilever beam-displacement: accessible quantum sensing

Benjamin J. Lawrie, Jacob L. Beckey, Raphael C. Pooser

Conference on Lasers and Electro-OpticsJan 1, 20190 citations

Enhancement of the phase-measurement sensitivity beyond the standard quantum limit by a nonlinear interferometer

Z. Y. Ou

A nonlinear interferometer uses nonlinear elements as beam splitters to split and to recombine optical waves for interference. As a result, the interference fringe size has a nonlinear dependence on the intensity of the field for phase sensing and leads to an enhanced phase signal. In this paper, a practical scheme of nonlinear interferometry for precision phase measurement is analyzed with parametric amplifiers as the nonlinear beam splitters. It is found that the signal due to phase shift is enhanced by a factor of the amplification gain as compared to a linear interferometer with the same phase-sensing light intensity while the quantum noise is kept at the vacuum level, thus, effectively increasing the signal-to-noise ratio (SNR) beyond the standard quantum limit. Furthermore, the scheme is not as sensitive to the detection loss as the linear scheme with a squeezed state for noise reduction. However, losses inside the interferometer limit the enhancement factor in SNR. We apply the concept to a Michelson interferometer but with parametric amplifiers involved for gravitational-wave detection. We find that effective power is increased by the gain of the amplifiers without actually increasing the cycling power inside the interferometer. Furthermore, the full benefits with squeezed input and variational output or the combination of a quantum nondemolition interferometer for sensitivity beyond the standard quantum limit apply here with even better results. Such a nonlinear interferometer will find wide applications in precision measurements.

Physical Review AFeb 14, 2012195 citations

Quantum metrology with parametric amplifier-based photon correlation interferometers

Florian Hudelist, Jia Kong, Cunjin Liu +3 more

Conventional interferometers usually utilize beam splitters for wave splitting and recombination. These interferometers are widely used for precision measurement. Their sensitivity for phase measurement is limited by the shot noise, which can be suppressed with squeezed states of light. Here we study a new type of interferometer in which the beam splitting and recombination elements are parametric amplifiers. We observe an improvement of 4.1±0.3 dB in signal-to-noise ratio compared with a conventional interferometer under the same operating condition, which is a 1.6-fold enhancement in rms phase measurement sensitivity beyond the shot noise limit. The improvement is due to signal enhancement. Combined with the squeezed state technique for shot noise suppression, this interferometer promises further improvement in sensitivity. Furthermore, because nonlinear processes are involved in this interferometer, we can couple a variety of different waves and form new types of hybrid interferometers, opening a door for many applications in metrology. Interferometers play a key role in precision measurements and metrology. Here, the authors demonstrate a new type of interferometer that replaces the standard beam splitter elements with parametric amplifiers, which provides enhanced performance compared with a Mach–Zehnder interferometer.

Nature CommunicationsJan 29, 2014438 citations

PHASE MEASUREMENTS WITH A TWO-MODE SQUEEZED STATE OF LIGHT.

Gupta, Prasoon

Introducing squeezed states of light into interferometers can increase the phase sensitivity of the device beyond the standard quantum limit (SQL). We discuss an SU(1,1) interferometer, where nonlinear optical elements replace the beam splitters in a Mach-Zehnder interferometer. A two-mode squeezed state of light is generated inside of such an interferometer. We talk about the phase sensitivities of an SU(1,1) interferometer with different detection schemes and their improvement over the SQL. We also discuss the concept of an optimal detection scheme for phase measurement in an interferometer. We describe a modification of the SU(1,1) interferometer which reduces the experimental complexities while giving the same phase sensitivity. We call the design a truncated SU(1,1) interferometer. We show our experimental results of 4 dB improvement in phase sensitivity over the SQL using a truncated SU(1,1) interferometer. We also compare the theoretical sensitivities of vacuum-seeded configurations of a conventional and a truncated SU(1,1) interferometer, and show our experimental results for the phase sensitivity of the truncated version. We explain the dependence of phase sensitivity on the measurement of squeezing. We talk about the methods to improve the measurement of squeezing in a 4-wave mixing experiment, and our efforts in implementing them. Finally, we mention our progress in measuring a big phase shift using an adaptive algorithm in the truncated SU(1,1) interferometer, and discuss the technicalities involved in big phase measurements.

Jan 1, 20190 citations