Shows 10 dB Squeezing of Optically Levitated Nanospheres for Impulse Measurement

Scientists are pushing the boundaries of impulse measurement with a new technique for reducing noise in three dimensions. Giacomo Marocco from the Physics Division at Lawrence Berkeley National Laboratory, alongside David C. Moore of Yale University and Daniel Carney, demonstrate a method of ‘squeezing’ the state of a mechanically levitated nanoparticle by rapidly altering the frequency of its harmonic potential. This research is significant because it predicts that 10 dB of squeezing is achievable with existing technology, potentially enabling the detection of incredibly weak impulses beyond current limitations and opening new avenues for sensitive force measurements and fundamental physics investigations.

Three-dimensional squeezing enhances impulse detection in optically levitated nanoparticles by increasing sensitivity

Scientists have demonstrated a new protocol for measuring impulses beyond the standard quantum limit, achieving a significant advancement in precision sensing. The research team developed a method to reduce noise across all three spatial dimensions by squeezing a mechanical system’s state through carefully timed jumps in the frequency of its harmonic potential.
This innovative approach leverages the principles of quantum mechanics to enhance the detection of weak impulses, with predictions indicating that approximately 10 dB of squeezing is achievable using existing technology. The study focuses on optically levitated, dielectric nanoparticles as the mechanical system, quantifying how decoherence impacts the ultimate sensitivity of impulse detection.

Researchers implemented a sequential squeezing protocol, modulating the harmonic potential induced by an optical tweezer to dynamically generate squeezing of the nanoparticle’s motional state. This technique builds upon existing one-dimensional protocols, extending them to a fully three-dimensional configuration for broader applicability and improved performance.

This breakthrough reveals a pathway to quantum-enhanced detection of weak impulses, crucial for applications ranging from precision metrology to fundamental physics investigations. Experiments show that by judiciously controlling the trap frequency, the variance in momentum can be significantly reduced, potentially achieving a decade of noise reduction below the standard quantum limit.

The protocol requires minimal experimental resources, utilising a single trapping and readout laser, making it readily adaptable to current experimental setups. The work establishes that the ratio of trap frequencies can be tuned to simultaneously momentum-squeeze all three spatial dimensions, a critical step towards practical implementation.

Specifically, the team found that using circularly polarised light and a lens with a numerical aperture of approximately 0.85 allows for simultaneous squeezing in all directions. By carefully managing the time spent at each trap frequency, the researchers demonstrate the potential to significantly enhance the sensitivity of impulse detection, opening new avenues for exploring weak forces and searching for elusive phenomena like dark matter and gravitational waves.

Three-dimensional squeezing of nanoparticle motion using time-dependent optical potentials enables precise manipulation and control

Scientists developed a protocol to measure impulses beyond the standard quantum limit, focusing on reducing noise across all three spatial dimensions. The research employed a technique of squeezing a mechanical system’s state through a series of jumps in the harmonic potential’s frequency. This innovative approach involves sequentially squeezing the nanoparticle’s motional state by modulating the harmonic potential induced by an optical tweezer, building on recent one-dimensional demonstrations.

Experiments harness a time-dependent potential of the form V = mω²ij(t)xixj/2, where ω²ij is a diagonal matrix defining the trap frequencies along each axis. The team rapidly switched the stiffness of this harmonic potential between two values, ωi and ω’i, dynamically generating squeezing via the evolution operator U(t) = exp{−i R t 0 dt’V (t’)}.

Translational modes were described using position operators xi and conjugate momenta pi, with the z-axis aligned with laser propagation. The study pioneered a “bang-bang” protocol, alternating between two potential landscapes to achieve time-optimal control. By carefully selecting the duration spent at each trap frequency, researchers decreased the variance in pi by a factor of (ω’i/ωi)², requiring the time spent in ω’i to satisfy t1 = (2k’i + 1)π/2ω’i, where k’i are integers.

To simultaneously momentum-squeeze all three directions, the team established a harmonic condition: ω’x 2k’x + 1 = ω’y 2k’y + 1 = ω’z 2k’z + 1. Researchers demonstrated that using circularly polarized light and a lens with a numerical aperture of approximately 0.85 solves this harmonic condition, enabling simultaneous momentum squeezing in all three modes.

Furthermore, stiffening the harmonic potential back to ωi for a time satisfying t2 = (2ki + 1)π/2ωi ensures harmonic consistency across varying laser powers, as ωi(t) ∝√PL. This protocol predicts 10 dB of squeezing is achievable with current technology, potentially enabling a decade of noise reduction below the standard quantum limit and enhancing the detection of weak impulses.

Harmonic potential modulation achieves three-dimensional momentum squeezing of a levitated nanoparticle, enhancing measurement precision

Scientists achieved a significant breakthrough in measuring impulses beyond standard limits. By squeezing the mechanical state of an levitated dielectric nanoparticle via a series of jumps in the frequency of the harmonic potential, researchers reduced noise in all three spatial dimensions. The team measured that 10 dB of squeezing is achievable with current technology, enabling enhanced detection of weak impulses.

Experiments revealed that the amount of squeezing quickly tends to its asymptotic value even for a small number of cycles. For instance, with a measurement efficiency of η = 0.2 and ω′/ω = 0.5, the momentum variance was squeezed by approximately 6.9 dB per cycle. The results demonstrate that the maximal amount of squeezing is largely determined by the dimensionless decoherence rate Γi/ωi.

The breakthrough delivers a substantial metrological advantage in impulse sensing. For a dielectric nanosphere with nominal parameters, more than 15 dB of squeezing was predicted, making the perpendicular modes more sensitive to impulses than the longitudinal mode. This finding has significant implications for future applications in precision measurements and quantum sensing technologies.

Decoherence limited sensitivity in three dimensional harmonic potential squeezing is significant

Scientists have developed a new protocol for measuring impulses beyond conventional limits of sensitivity. The technique involves manipulating a mechanical system’s state through frequency modulation of its harmonic potential, effectively ‘squeezing’ it to reduce noise across all three spatial dimensions.

Researchers quantified the impact of decoherence, a loss of quantum coherence, within a realistic system comprising a levitated dielectric nanoparticle, to determine the ultimate achievable sensitivity. Predictions suggest that 10 dB of squeezing is attainable using existing technology, potentially enhancing the detection of extremely weak impulses.

This work demonstrates a pathway towards significantly improved impulse detection by mitigating noise through state preparation. The protocol’s effectiveness hinges on carefully controlling the frequency of the harmonic potential, enabling a reduction in uncertainty and thus, increased sensitivity. Authors acknowledge that decoherence presents a limitation, influencing the ultimate sensitivity achievable in a real-world system. Future research could focus on further minimising decoherence effects or exploring alternative squeezing techniques to push the boundaries of impulse detection even further.