Biological measurement beyond the quantum limit
TL;DR: In this paper, the authors used squeezed light to track the constituents of yeast cells with a performance that overcomes the quantum noise limit, which allows for the utilization of low optical power, which helps to minimize cell damage.
Abstract: Researchers use squeezed light to track the constituents of yeast cells with a performance that overcomes the quantum noise limit. This approach allows for the utilization of low optical power, which helps to minimize cell damage.
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Abstract: "Quantum sensing" describes the use of a quantum system, quantum properties or quantum phenomena to perform a measurement of a physical quantity Historical examples of quantum sensors include magnetometers based on superconducting quantum interference devices and atomic vapors, or atomic clocks More recently, quantum sensing has become a distinct and rapidly growing branch of research within the area of quantum science and technology, with the most common platforms being spin qubits, trapped ions and flux qubits The field is expected to provide new opportunities - especially with regard to high sensitivity and precision - in applied physics and other areas of science In this review, we provide an introduction to the basic principles, methods and concepts of quantum sensing from the viewpoint of the interested experimentalist
1,878 citations
TL;DR: This Perspective is intended as a guidebook for both experimentalists and theorists working on systems, which exhibit anomalous diffusion, and pays special attention to the ergodicity breaking parameters for the different anomalous stochastic processes.
Abstract: Modern microscopic techniques following the stochastic motion of labelled tracer particles have uncovered significant deviations from the laws of Brownian motion in a variety of animate and inanimate systems. Such anomalous diffusion can have different physical origins, which can be identified from careful data analysis. In particular, single particle tracking provides the entire trajectory of the traced particle, which allows one to evaluate different observables to quantify the dynamics of the system under observation. We here provide an extensive overview over different popular anomalous diffusion models and their properties. We pay special attention to their ergodic properties, highlighting the fact that in several of these models the long time averaged mean squared displacement shows a distinct disparity to the regular, ensemble averaged mean squared displacement. In these cases, data obtained from time averages cannot be interpreted by the standard theoretical results for the ensemble averages. Here we therefore provide a comparison of the main properties of the time averaged mean squared displacement and its statistical behaviour in terms of the scatter of the amplitudes between the time averages obtained from different trajectories. We especially demonstrate how anomalous dynamics may be identified for systems, which, on first sight, appear to be Brownian. Moreover, we discuss the ergodicity breaking parameters for the different anomalous stochastic processes and showcase the physical origins for the various behaviours. This Perspective is intended as a guidebook for both experimentalists and theorists working on systems, which exhibit anomalous diffusion.
1,390 citations
TL;DR: The continuous position measurement of a solid-state, optomechanical system fabricated from a silicon microchip and comprising a micromechanical resonator coupled to a nanophotonic cavity is described, observing squeezing of the reflected light’s fluctuation spectrum at a level 4.5 ± 0.2 per cent below that of vacuum noise.
Abstract: Monitoring a mechanical object’s motion, even with the gentle
touch of light, fundamentally alters its dynamics. The experimental
manifestation of this basic principle of quantum mechanics, its
link to the quantum nature of light and the extension of quantum
measurement to the macroscopic realm have all received extensive
attention over the past half-century. The use of squeezed light, with
quantum fluctuations below that of the vacuum field, was proposed
nearly three decades ago
as a means of reducing the optical read-out
noise in precision force measurements. Conversely, it has also been proposed that a continuous measurement of a mirror’s position with
light may itself give rise to squeezed light. Such squeezed-light generation has recently been demonstrated in a system of ultracold
gas-phase atoms whose centre-of-mass motion is analogous to the
motion of a mirror. Here we describe the continuous position measurement of a solid-state, optomechanical system fabricated from a
silicon microchip and comprising a micromechanical resonator
coupled to a nanophotonic cavity. Laser light sent into the cavity is
used to measure the fluctuations in the position of the mechanical
resonator at a measurement rate comparable to its resonance frequency and greater than its thermal decoherence rate. Despite the
mechanical resonator’s highly excited thermal state (10^4
phonons),
we observe, through homodyne detection, squeezing of the reflected
light’s fluctuation spectrum at a level 4.5 ± 0.2 percent below that of
vacuum noise over a bandwidth of a few megahertz around the
mechanical resonance frequency of 28megahertz. With further
device improvements, on-chip squeezing at significant levels should
be possible, making such integrated microscale devices well suited
for precision metrology applications.
512 citations
TL;DR: An atomic clock measurement with a quantum enhancement of 10.5 ± 0.3 decibels (11-fold) is demonstrated, limited by the phase noise of the microwave source.
Abstract: Quantum metrology uses quantum entanglement--correlations in the properties of microscopic systems--to improve the statistical precision of physical measurements. When measuring a signal, such as the phase shift of a light beam or an atomic state, a prominent limitation to achievable precision arises from the noise associated with the counting of uncorrelated probe particles. This noise, commonly referred to as shot noise or projection noise, gives rise to the standard quantum limit (SQL) to phase resolution. However, it can be mitigated down to the fundamental Heisenberg limit by entangling the probe particles. Despite considerable experimental progress in a variety of physical systems, a question that persists is whether these methods can achieve performance levels that compare favourably with optimized conventional (non-entangled) systems. Here we demonstrate an approach that achieves unprecedented levels of metrological improvement using half a million (87)Rb atoms in their 'clock' states. The ensemble is 20.1 ± 0.3 decibels (100-fold) spin-squeezed via an optical-cavity-based measurement. We directly resolve small microwave-induced rotations 18.5 ± 0.3 decibels (70-fold) beyond the SQL. The single-shot phase resolution of 147 microradians achieved by the apparatus is better than that achieved by the best engineered cold atom sensors despite lower atom numbers. We infer entanglement of more than 680 ± 35 particles in the atomic ensemble. Applications include atomic clocks, inertial sensors, and fundamental physics experiments such as tests of general relativity or searches for electron electric dipole moment. To this end, we demonstrate an atomic clock measurement with a quantum enhancement of 10.5 ± 0.3 decibels (11-fold), limited by the phase noise of our microwave source.
451 citations
ICFO – The Institute of Photonic Sciences1, Ludwig Maximilian University of Munich2, Max Planck Society3, University of Amsterdam4, ETH Zurich5, Free University of Berlin6, University of Geneva7, Technische Universität München8, University of Strathclyde9, Leibniz University of Hanover10, German National Metrology Institute11, University of Oxford12, Saarland University13
TL;DR: In this article, the authors present an updated summary of the roadmap of quantum technologies (QT) and present an overview of the current state-of-the-art quantum technologies.
Abstract: Within the last two decades, quantum technologies (QT) have made tremendous progress, moving from Nobel Prize award-winning experiments on quantum physics (1997: Chu, Cohen-Tanoudji, Phillips; 2001: Cornell, Ketterle, Wieman; 2005: Hall, Hansch-, Glauber; 2012: Haroche, Wineland) into a cross-disciplinary field of applied research. Technologies are being developed now that explicitly address individual quantum states and make use of the 'strange' quantum properties, such as superposition and entanglement. The field comprises four domains: quantum communication, where individual or entangled photons are used to transmit data in a provably secure way; quantum simulation, where well-controlled quantum systems are used to reproduce the behaviour of other, less accessible quantum systems; quantum computation, which employs quantum effects to dramatically speed up certain calculations, such as number factoring; and quantum sensing and metrology, where the high sensitivity of coherent quantum systems to external perturbations is exploited to enhance the performance of measurements of physical quantities. In Europe, the QT community has profited from several EC funded coordination projects, which, among other things, have coordinated the creation of a 150-page QT Roadmap (http://qurope.eu/h2020/qtflagship/roadmap2016). This article presents an updated summary of this roadmap.
443 citations
References
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TL;DR: This work has shown that conventional bounds to the precision of measurements such as the shot noise limit or the standard quantum limit are not as fundamental as the Heisenberg limits and can be beaten using quantum strategies that employ “quantum tricks” such as squeezing and entanglement.
Abstract: Quantum mechanics, through the Heisenberg uncertainty principle, imposes limits on the precision of measurement. Conventional measurement techniques typically fail to reach these limits. Conventional bounds to the precision of measurements such as the shot noise limit or the standard quantum limit are not as fundamental as the Heisenberg limits and can be beaten using quantum strategies that employ “quantum tricks” such as squeezing and entanglement.
2,421 citations
TL;DR: These techniques are described and illustrated with examples highlighting current capabilities and limitations of single-molecule force spectroscopy.
Abstract: Single-molecule force spectroscopy has emerged as a powerful tool to investigate the forces and motions associated with biological molecules and enzymatic activity. The most common force spectroscopy techniques are optical tweezers, magnetic tweezers and atomic force microscopy. Here we describe these techniques and illustrate them with examples highlighting current capabilities and limitations.
2,155 citations
TL;DR: Trapping and manipulation of single live motile bacteria and Escherichia coli bacteria were demonstrated in a high-resolution microscope at powers of a few milliwatts.
Abstract: Optical trapping and manipulation of viruses and bacteria by laser radiation pressure were demonstrated with single-beam gradient traps. Individual tobacco mosaic viruses and dense oriented arrays of viruses were trapped in aqueous solution with no apparent damage using approximately 120 milliwatts of argon laser power. Trapping and manipulation of single live motile bacteria and Escherichia coli bacteria were also demonstrated in a high-resolution microscope at powers of a few milliwatts.
2,107 citations
TL;DR: It is found that kinesin moves with 8-nm steps, similar to biological motors that move with regular steps.
Abstract: Do biological motors move with regular steps? To address this question, we constructed instrumentation with the spatial and temporal sensitivity to resolve movement on a molecular scale. We deposited silica beads carrying single molecules of the motor protein kinesin on microtubules using optical tweezers and analysed their motion under controlled loads by interferometry. We find that kinesin moves with 8-nm steps.
1,829 citations
TL;DR: A new in vitro assay using a feedback enhanced laser trap system allows direct measurement of force and displacement that results from the interaction of a single myosin molecule with a single suspended actin filament.
Abstract: A new in vitro assay using a feedback enhanced laser trap system allows direct measurement of force and displacement that results from the interaction of a single myosin molecule with a single suspended actin filament. Discrete stepwise movements averaging 11 nm were seen under conditions of low load, and single force transients averaging 3-4 pN were measured under isometric conditions. The magnitudes of the single forces and displacements are consistent with predictions of the conventional swinging-crossbridge model of muscle contraction.
1,814 citations