Probing Quantum Correlation in Two Coupled Cavity Optomechanics

Why are classical theories often sufficient to describe the physics of our world even though everything around us is entirely composed of microscopic quantum systems? The boundary between these two fundamentally dissimilar theories remains an unsolved problem in modern physics. Position measurements of small objects allow us to probe the area where the classical approximation breaks down. In quantum mechanics, Heisenbergâ s uncertainty principle dictates that any measurement of the position must be accompanied by measurement induced back-action---in this case manifested as an uncertainty in the momentum. In recent years, cavity optomechanics has become a powerful tool to perform precise position measurements and investigate their fundamental limitations. The utilization of optical micro-cavities greatly enhances the interaction between light and state-of-the-art nanomechanical oscillators. Therefore, quantum mechanical phenomena have been successfully observed in systems far beyond the microscopic world. In such a cavity optomechanical system, the fluctuations in the position of the oscillator are transduced onto the phase of the light, while fluctuations in the amplitude of the light disturb the momentum of the oscillator during the measurement. As a consequence, correlations are established between the amplitude and phase quadrature of the probe light. However, so far, observation of quantum effects has been limited exclusively to cryogenic experiments, and access to the quantum regime at room temperature has remained an elusive goal because the overwhelming amount of thermal motion masks the weak quantum effects. This thesis describes the engineering of a high-performance cavity optomechanical device and presents experimental results showing, for the first time, the broadband effects of quantum back-action at room temperature. The device strongly couples mechanical and optical modes of exceptionally high quality factors to provide a measurement sensitivity $\sim\!10^4$ times below the requirement to resolve the zero-point fluctuations of the mechanical oscillator. The quantum back-action is then observed through the correlations created between the probe light and the motion of the nanomechanical oscillator. A so-called â variational measurementâ , which detects the transmitted light in a homodyne detector tuned close to the amplitude quadrature, resolves the quantum noise due to these correlations at the level of 10\% of the thermal noise over more than an octave of Fourier frequencies around mechanical resonance. Moreover, building on this result, an additional experiment demonstrates the ability to achieve quantum enhanced metrology. In this case, the generated quantum correlations are used to cancel quantum noise in the measurement record, which then leads to an improved relative signal-to-noise ratio in measurements of an external force. In conclusion, the successful observation of broadband quantum behavior on a macroscopic object at room temperature is an important milestone in the field of cavity optomechanics. Specifically, this result heralds the rise of optomechanical systems as a platform for quantum physics at room temperature and shows promise for generation of ponderomotive squeezing in room-temperature interferometers.Why are classical theories often sufficient to describe the physics of our world even though everything around us is entirely composed of microscopic quantum systems? The boundary between these two fundamentally dissimilar theories remains an unsolved problem in modern physics. Position measurements of small objects allow us to probe the area where the classical approximation breaks down. In quantum mechanics, Heisenbergâ s uncertainty principle dictates that any measurement of the position must be accompanied by measurement induced back-action---in this case manifested as an uncertainty in the momentum. In recent years, cavity optomechanics has become a powerful tool to perform precise position measurements and investigate their fundamental limitations. The utilization of optical micro-cavities greatly enhances the interaction between light and state-of-the-art nanomechanical oscillators. Therefore, quantum mechanical phenomena have been successfully observed in systems far beyond the microscopic world. In such a cavity optomechanical system, the fluctuations in the position of the oscillator are transduced onto the phase of the light, while fluctuations in the amplitude of the light disturb the momentum of the oscillator during the measurement. As a consequence, correlations are established between the amplitude and phase quadrature of the probe light. However, so far, observation of quantum effects has been limited exclusively to cryogenic experiments, and access to the quantum regime at room temperature has remained an elusive goal because the overwhelming amount of thermal motion masks the weak quantum effects. This thesis describes the engineering of a high-performance cavity optomechanical device and presents experimental results showing, for the first time, the broadband effects of quantum back-action at room temperature. The device strongly couples mechanical and optical modes of exceptionally high quality factors to provide a measurement sensitivity $\sim\!10^4$ times below the requirement to resolve the zero-point fluctuations of the mechanical oscillator. The quantum back-action is then observed through the correlations created between the probe light and the motion of the nanomechanical oscillator. A so-called â variational measurementâ , which detects the transmitted light in a homodyne detector tuned close to the amplitude quadrature, resolves the quantum noise due to these correlations at the level of 10\% of the thermal noise over more than an octave of Fourier frequencies around mechanical resonance. Moreover, building on this result, an additional experiment demonstrates the ability to achieve quantum enhanced metrology. In this case, the generated quantum correlations are used to cancel quantum noise in the measurement record, which then leads to an improved relative signal-to-noise ratio in measurements of an external force. In conclusion, the successful observation of broadband quantum behavior on a macroscopic object at room temperature is an important milestone in the field of cavity optomechanics. Specifically, this result heralds the rise of optomechanical systems as a platform for quantum physics at room temperature and shows promise for generation of ponderomotive squeezing in room-temperature interferometers.

Jan 1, 20170 citations

Quantum Correlations in Molecular Cavity Optomechanics

Philippe Djorwé, Kongkui Berinyuy Emale, D. R. K. Massembele +4 more

Jan 1, 20250 citations

Hybrid spin-optomechanical control of induced transparency in coupled cavity systems

Fatima Kosar, Soma Bashir, Nusrat Riaz +2 more

Abstract Optomechanics has become a very active area of research in recent years and has attracted significant interest in both theoretical and experimental studies. In this work, we theoretically investigate optomechanically induced transparency (OMIT) using a hybrid system consisting of two coupled optical cavities, each interacting with a spin ensemble. The cavities are coherently driven by a strong control field and a weak probe field. We analytically calculate the transmission spectrum of the coupled spin–cavity system and analyze the dynamics of the system. The obtained transmission response shows clear signatures of multi-window OMIT, which arises from coherent interference between the hybridized normal modes. Our results indicate that the presence of spin ensembles in both cavities significantly enhances the transparency behavior and provides additional tunable parameters to control the OMIT windows. In particular, the transmission spectrum and the shape of the transparency profile can be controlled by the spin–cavity interaction and the inter-cavity coupling strength J . Furthermore, the inter-cavity tunneling rate, spin decoherence, and spin–cavity coupling strength strongly influence the transparency properties. Overall, this study highlights the potential of spin-based multi-cavity optomechanical systems for coherent optical control and tunable quantum interference.Abstract Optomechanics has become a very active area of research in recent years and has attracted significant interest in both theoretical and experimental studies. In this work, we theoretically investigate optomechanically induced transparency (OMIT) using a hybrid system consisting of two coupled optical cavities, each interacting with a spin ensemble. The cavities are coherently driven by a strong control field and a weak probe field. We analytically calculate the transmission spectrum of the coupled spin–cavity system and analyze the dynamics of the system. The obtained transmission response shows clear signatures of multi-window OMIT, which arises from coherent interference between the hybridized normal modes. Our results indicate that the presence of spin ensembles in both cavities significantly enhances the transparency behavior and provides additional tunable parameters to control the OMIT windows. In particular, the transmission spectrum and the shape of the transparency profile can be controlled by the spin–cavity interaction and the inter-cavity coupling strength J . Furthermore, the inter-cavity tunneling rate, spin decoherence, and spin–cavity coupling strength strongly influence the transparency properties. Overall, this study highlights the potential of spin-based multi-cavity optomechanical systems for coherent optical control and tunable quantum interference.

Journal of Physics B Atomic Molecular and Optical PhysicsJun 11, 20260 citations

Fano resonance and slow light in hybrid optomechanics mediated by a two-level system

Cheng Jiang, Lei Jiang, Hualing Yu +3 more

We study the Fano resonance and slow light in a hybrid optomechanical system, where a mechanical resonator is coupled to a cavity via radiation pressure and to a two-level system (qubit) via the Jaynes-Cummings coupling. The absorption spectra of the weak probe field can exhibit a series of asymmetric Fano line shapes when the frequency of the strong control field varies. The positions of the double Fano resonances can be determined by the cavity--control-field detuning, the qubit-resonator coupling strength, and the transition frequency of the qubit. Furthermore, the transparency windows in the probe transmission spectrum are accompanied by the rapid normal phase dispersion, which indicates the slow light effect. We find that the group delay of the transmitted probe field can be tuned by the frequency and amplitude of the control field and is inversely proportional to the decay rate of the qubit.We study the Fano resonance and slow light in a hybrid optomechanical system, where a mechanical resonator is coupled to a cavity via radiation pressure and to a two-level system (qubit) via the Jaynes-Cummings coupling. The absorption spectra of the weak probe field can exhibit a series of asymmetric Fano line shapes when the frequency of the strong control field varies. The positions of the double Fano resonances can be determined by the cavity--control-field detuning, the qubit-resonator coupling strength, and the transition frequency of the qubit. Furthermore, the transparency windows in the probe transmission spectrum are accompanied by the rapid normal phase dispersion, which indicates the slow light effect. We find that the group delay of the transmitted probe field can be tuned by the frequency and amplitude of the control field and is inversely proportional to the decay rate of the qubit.

Physical Review ANov 8, 201759 citations

\sim\!10^4

times below the requirement to resolve the zero-point fluctuations of the mechanical oscillator. The quantum back-action is then observed through the correlations created between the probe light and the motion of the nanomechanical oscillator. A so-called â variational measurementâ , which detects the transmitted light in a homodyne detector tuned close to the amplitude quadrature, resolves the quantum noise due to these correlations at the level of 10\% of the thermal noise over more than an octave of Fourier frequencies around mechanical resonance. Moreover, building on this result, an additional experiment demonstrates the ability to achieve quantum enhanced metrology. In this case, the generated quantum correlations are used to cancel quantum noise in the measurement record, which then leads to an improved relative signal-to-noise ratio in measurements of an external force. In conclusion, the successful observation of broadband quantum behavior on a macroscopic object at room temperature is an important milestone in the field of cavity optomechanics. Specifically, this result heralds the rise of optomechanical systems as a platform for quantum physics at room temperature and shows promise for generation of ponderomotive squeezing in room-temperature interferometers.