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Strange weak values of photon number operators in the optomechanical interaction

Sergio Carrasco, Miguel Orszag

Published Apr 26, 2018• 0 citations
OpenAlex

Abstract

An interferometric experiment is proposed in order to measure the radiation force exerted by a single photon on a nano mechanical oscillator placed in the middle of a Fabry-P\'erot cavity. The force is measured by observing the shift given to the probability density function of the position of the oscillator, using weak measurements and post-selection of photons. We show that this shift is proportional to the weak value of the operator that accounts for the difference of photons between both sides of the cavity. For single-photon states, this operator has eigenvalues 1 or -1, depending on the side of the cavity in which is the photon, but the weak value can exceed by far this range. Thus, by preparing and post-selecting the photon in two nearly orthogonal states the weak value is increased and the radiation effect of a single photon turns out to be much larger than the pressure exerted by a photon without post-selection. This opens the possibility to study weak values of number operators in optomechanics and the radiation effect in pre- and post-selected ensembles.

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Abstract An interferometric arrangement is proposed in which the technique of weak value amplification is implemented in order to enlarge the effect of a single photon on the quadratures of a movable mirror of an optical cavity. The photon interacts weakly with the mirror via radiation pressure and is postselected in the dark port of the interferometer. The real and imaginary parts of weak values of angular momentum type photonic operators produce an amplification of the mirror quadratures, which is large as compared to the scenario in which all photons are taken into consideration, i.e. when no postselection is performed. The effect is studied both for a mirror initialized in a thermal and coherent states. For a thermal state, the weak value amplification effect is boosted with the number of particles of the mirror, which occurs due to the imaginary part of the weak values.

arXiv:2202.00750•Physica Scripta•May 31, 2022•1 citation
An interferometric experiment is proposed in order to measure the radiation force exerted by a single photon on a nano mechanical oscillator placed in the middle of a Fabry-P'erot cavity. The force is measured by observing the shift given to the probability density function of the position of the oscillator, using weak measurements and post-selection of photons. We show that this shift is proportional to the weak value of the operator that accounts for the difference of photons between both sides of the cavity. For single-photon states, this operator has eigenvalues 1 or -1, depending on the side of the cavity in which is the photon, but the weak value can exceed by far this range. Thus, by preparing and post-selecting the photon in two nearly orthogonal states the weak value is increased and the radiation effect of a single photon turns out to be much larger than the pressure exerted by a photon without post-selection. This opens the possibility to study weak values of number operators in optomechanics and the radiation effect in pre- and post-selected ensembles.
An experimental proposal is presented in which dark port postselection together with weak measurements are used to enlarge the radiation pressure effect of a single photon on a mechanical oscillator placed in the middle of a Fabry-P\'erot cavity and initialized in the ground state. By preparing and postselecting the photon (the system) in two quasiorthogonal states, the weak value of the radiation force operator can lie outside the eigenvalue spectrum, producing a large shift on the wave function of the mechanical oscillator (the measuring device) in the position representation. Consequently, the effect of a single photon on the average position of the oscillator can be amplified as compared to the effect caused by a photon without postselection, i.e., only preselected. The strong measurement scenario is also analyzed. In this case, a higher amplification effect is achieved and the mean position of the oscillator can reach the level of the zero-point fluctuations, but the postselection probabilities are smaller. Finally, the situation in which the oscillator starts in a thermal equilibrium state is studied. In this case, the amplification of the average position remains the same, i.e., proportional to the weak value, but the signal-to-noise ratio is reduced by a factor that depends on the average number of thermal phonons.
In this article we present an experimental proposal for quantum enhanced estimation of optomechanical parameters. The precision of the estimation is improved by using the technique of weak value amplification, which can enlarge the radiation pressure effect of a single-photon on a nano/micro mechanical oscillator. This task is accomplished by using two interferometric setups. Single-photon pulses are sent through one interferometer, producing a maximally path entangled state which drives the cavity optomechanical system. The photons are then postselected in one of the detectors in the output. A second interferometer, whose operation is triggered by every successful postselection, performs an optical measurement of the phase shift generated by the optomechanical system on a classical beam, which encodes the information of the optomechanical parameters. In the presence of fully time-correlated noise, we show that the Fisher information is improved as compared to a standard measurement that employs no postselection.
Abstract We have studied the amplification in displacement of the mechanical mirror in a simple optomechanical system. Here photon number acts as system and the mirror acts as the meter. In the weak coupling condition, post selection of the photon number operator enhance the value of mirror displacement. The displacement of the mirror depends on the weak value of the photon number operator and on the value of relative phase(φ) between the pre and post selected states. Amplification of the mirror can be seen for maximum coupling strength(.25Ω m ) in weak coupling criteria for optomechanical systems, Ωm being the mechanical frequency.
Abstract Most studies for postselected weak measurement in optomechanical system focus on using a single photon as a measured system. However, we find that using weak coherent light instead of a single photon can also amplify the mirror’s position displacement of one photon. In the weak value amplification (WVA) regime, the weak value of one photon can lie outside the eigenvalue spectrum, proportional to the difference of the mirror’s position displacement between the successful and failed postselection and its successful postselection probability is dependent of the mean photon number of the coherent light and improved by adjusting it accordingly. Outside the WVA regime, the amplification limit can reach the level of the vacuum fluctuations, and when the mean photon number and the optomechanical coupling parameter are selected appropriately, its successful postselection probability becomes higher, which is beneficial to observe the maximum amplification value under the current experimental conditions. This result breaks the constraint that it is difficult to detect outside the WVA regime. This opens up a new regime for the study of a single photon nonlinearity in optomechanical system.
Cavity optomechanics originated from the research of interferometric detection of gravitational waves, and later became a fast-growing area of techniques and approaches ranging from the fields of atomic, molecular, and optical physics to nano-science and condensed matter physics as well. Recently, it focused on the exploration of operating mechanical oscillators deep in the quantum regime, with an interest ranging from quantum-classical interface tests to high-precision quantum metrology. In this paper, recent theoretical work of our group in the field of quantum measurement with cavity optomechanical systems is reviewed. We explore the quantum measurement theory and its applications with several unconventional cavity optomechanical schemes working in the quantum regime. This review covers the basics of quantum noises in the cavity optomechanical setups and the resulting standard quantum limit of precision displacement and force measurement. Three novel quantum measurement proposals based on the hybrid optomechanical system are introduced. First, we describe a quantum back-action insulated weak force sensor. It is realized by forming a quantum-mechanics-free subsystem with two optomechanical oscillators of reversed effective mass. Then we introduce a role-reversed atomic optomechanical system which enables the preparation and the quantum tomography of a variety of non-classical states of atoms. In this system, the cavity field acts as a mechanical oscillator driven by the radiation pressure force from an ultracold atomic field. In the end, we recommend a multimode optomechanical transducer that can detect intensities significantly below the single-photon level via adiabatic transfer of the microwave signal to the optical frequency domain. These proposals demonstrate the possible applications of optomechanical devices in understanding of quantum-classical crossover and in achieving quantum measurement limit.
Abstract An interferometric arrangement is proposed in which the technique of weak value amplification is implemented in order to enlarge the effect of a single photon on the quadratures of a movable mirror of an optical cavity. The photon interacts weakly with the mirror via radiation pressure and is postselected in the dark port of the interferometer. The real and imaginary parts of weak values of angular momentum type photonic operators produce an amplification of the mirror quadratures, which is large as compared to the scenario in which all photons are taken into consideration, i.e. when no postselection is performed. The effect is studied both for a mirror initialized in a thermal and coherent states. For a thermal state, the weak value amplification effect is boosted with the number of particles of the mirror, which occurs due to the imaginary part of the weak values.