Ground-State Cooling and High-Fidelity Quantum Transduction via Parametrically Driven Bad-Cavity Optomechanics

Optomechanical Microwave-to-Optical Photon Transducer Chips: Empowering the Quantum Internet Revolution

The first quantum revolution has brought us the classical Internet and information technology. Today, as technology advances rapidly, the second quantum revolution quietly arrives, with a crucial moment for quantum technology to establish large-scale quantum networks. However, solid-state quantum bits (such as superconducting and semiconductor qubits) typically operate in the microwave frequency range, making it challenging to transmit signals over long distances. Therefore, there is an urgent need to develop quantum transducer chips capable of converting microwaves into optical photons in the communication band, since the thermal noise of optical photons at room temperature is negligible, rendering them an ideal information carrier for large-scale spatial communication. Such devices are important for connecting different physical platforms and efficiently transmitting quantum information. This paper focuses on the fast-developing field of optomechanical quantum transducers, which has flourished over the past decade, yielding numerous advanced achievements. We categorize transducers based on various mechanical resonators and discuss their principles of operation and their achievements. Based on existing research on optomechanical transducers, we compare the parameters of several mechanical resonators and analyze their advantages and limitations, as well as provide prospects for the future development of quantum transducers.

Continuous Optical-to-Mechanical Quantum State Transfer in the Unresolved Sideband Regime

Optical-to-mechanical quantum state transfer is an important capability for future quantum networks, quantum communication, and distributed quantum sensing. However, existing continuous state transfer protocols operate in the resolved sideband regime, necessitating a high-quality optical cavity and a high mechanical resonance frequency. Here, we propose a continuous protocol that operates in the unresolved sideband regime. The protocol is based on feedback cooling, can be implemented with current technology, and is able to transfer non-Gaussian quantum states with high fidelity. Our protocol significantly expands the kinds of optomechanical devices for which continuous optical-to-mechanical state transfer is possible, paving the way toward quantum technological applications and the preparation of macroscopic superpositions to test the fundamentals of quantum science.

Robust quantum state transfer by optimal invariant-based reverse engineering

Shortening the operation time of implementing scheme and reducing the influence of harmful factors have always been the research objectives pursued by people. Based on invariant-based reverse engineering, we present a general scheme for implementing robust population transfer in a three-level system via optimal shortcut to adiabatic passage. The systematic error sensitivity is introduced to measure the robustness of the process. The smooth Rabi frequencies are expressed with some coefficients, which are also related to the systematic error sensitivity and the population of intermediate state. When the amplitude of control field is given, the transfer can be optimized within as small systematic error sensitivity as possible, i.e., the robustness against systematic errors is further improved by choosing suitable correlation coefficient. Additionally, we apply the technique to achieve robust excitation fluctuation transfer between two membranes in an optomechanical system. The relation between the fidelity of excitation fluctuation transfer and variation of effective optomechanical coupling strengths is analysed. Numerical result shows that the fidelity keeps over 0.95 even if the coupling strengths deviates from 20% of the theoretical value. Moreover, comparison with existing literature [Opt. Express29, 7998 (2021)10.1364/OE.417343], the proposed scheme possesses stronger robustness against variations of effective optomechanical coupling strengths and lower population of unwanted states. The idea may provide a promising approach for quantum information processing.

Cooling of mechanical resonator in a hybrid intracavity squeezing optomechanical system

A hybrid intracavity squeezing optomechanical cooling system, in which an auxiliary cavity couples to an optomechanical cavity with a nonlinear medium inside it, is proposed to realize the ground state cooling of the mechanical resonator in the highly unresolved sideband regime. We demonstrate that the quantum backaction heating can be suppressed perfectly by the intracavity squeezing, and the cooling process can be further promoted by adjusting the tunnel coupling between the coupled cavities. The scheme has good performance in resisting the environmental thermal noise and better tolerance for the auxiliary cavity quality factor and provides the possibility for the quantum manipulation of the mechanical resonator with large mass and low frequency.

Beating the 3 dB Limit for Intracavity Squeezing and Its Application to Nondemolition Qubit Readout

While the squeezing of a propagating field can, in principle, be made arbitrarily strong, the cavity-field squeezing is subject to the well-known 3 dB limit, and thus has limited applications. Here, we propose the use of a fully quantum degenerate parametric amplifier (DPA) to beat this squeezing limit. Specifically, we show that by simply applying a two-tone driving to the signal mode, the pump mode can, counterintuitively, be driven by the photon loss of the signal mode into a squeezed steady state with, in principle, an arbitrarily high degree of squeezing. Furthermore, we demonstrate that this intracavity squeezing can increase the signal-to-noise ratio of longitudinal qubit readout exponentially with the degree of squeezing. Correspondingly, an improvement of the measurement error by many orders of magnitude can be achieved even for modest parameters. In stark contrast, using intracavity squeezing of the semiclassical DPA cannot practically increase the signal-to-noise ratio and thus improve the measurement error. Our results extend the range of applications of DPAs and open up new opportunities for modern quantum technologies.

Parametrically enhanced interactions and nonreciprocal bath dynamics in a photon-pressure Kerr amplifier

Photon-pressure coupling between two superconducting circuits is a promising platform for investigating radiation-pressure coupling in distinct parameter regimes and for the development of radio-frequency (RF) quantum photonics and quantum-limited RF sensing. Here, we implement photon-pressure coupling between two superconducting circuits, one of which can be operated as a parametric amplifier. We demonstrate a Kerr-based enhancement of the photon-pressure single-photon coupling rate and an increase of the cooperativity by one order of magnitude in the amplifier regime. In addition, we observe that the intracavity amplification reduces the measurement imprecision of RF signal detection. Last, we demonstrate that RF mode sideband cooling is unexpectedly not limited to the effective amplifier mode temperature arising from quantum noise amplification, which we interpret in the context of nonreciprocal heat transfer between the two circuits. Our results demonstrate how Kerr amplification can be used as resource for enhanced photon-pressure systems and Kerr cavity optomechanics.

Spectral response of vibrational polaritons in an optomechanical cavity

Vibrational strong coupling provides a convenient way to modify the energy of molecular vibrations and to explore controlling chemical reactivity. In this work, we theoretically report the various vibrational anharmonicities that modulate the dynamics of optomechanically coupled W(CO)6-cavity. The optomechanical free-space cavity consists of movable photonic crystal (PhC) membrane, which creates the photonic bound states to interact with the molecular vibration. This coupled system is used for realizing strong optomechanical dispersive or dissipative type coupling, which provides a platform to explore the new regimes of the optomechanical interaction. The addition of different strong coupling and mechanical (nuclear) anharmonicities to the optical cavity establishes the modified splitting dynamics in the absorption spectrum and shows that the ground-state bleach of coupled W(CO)6- cavity has a broad, multisigned spectral response. This work points out the possibility of systematic and predictive modification of the multimode spectroscopy of optomechanical W(CO)6-cavity polariton system.

Simultaneous ground-state cooling of identical mechanical oscillators by Lyapunov control

The simultaneous cooling of multiple mechanical oscillators in the cavity optomechanical system has aroused people's attention and may be applicable in the quantum information process. In this paper, a scheme to realize the simultaneous ground-state cooling of two identical mechanical oscillators is proposed, where the frequency of one of the oscillators is designed according to Lyapunov control. By this method, the dark mode can effectively couple with the bright mode so that the two identical oscillators can be simultaneously cooled to their ground state. Extending this scheme into multiple identical mechanical oscillators, we show that simultaneous cooling can also be achieved.

Improving the Stochastic Feedback Cooling of a Mechanical Oscillator Using a Degenerate Parametric Amplifier

Cooling of a macroscopic mechanical resonator to extremely low temperatures is a necessary condition to observe a variety of macroscopic quantum phenomena. Here, we study the stochastic feedback cooling of a mechanical resonator in an optomechanical system with a degenerate optical parametric amplifier (OPA). In the bad-cavity limit, we find that the OPA can enhance the cooling of the movable mirror in the stochastic feedback cooling scheme. The movable mirror can be cooled from 132 mK to 0.033 mK, which is lower than that without the OPA by a factor of about 5.

Tunable microwave-optical entanglement and conversion in multimode electro-opto-mechanics

We study tunable double-channel microwave-optical (M-O) entanglement and coherent conversion by controlling the quantum interference effect. This is realized in a two-mechanical-mode electro-opto-mechanical (EOM) system, in which two mechanical resonators (MRs) are coupled with each other by phase-dependent phonon-phonon interaction, and link the interaction between the microwave and optical cavity. It's demonstrated that the mechanical coupling between two MRs leads to the interference of two pathways of electro-opto-mechanical interaction, which can generate the tunable double-channel phenomena in comparison with a typical three-mode EOM system. In particular, by tuning of phonon-phonon interaction and couplings between cavities with MRs, we can not only steer the switch from the M-O interaction with a single channel to that of the double-channel, but also modulate the entanglement and conversion characteristics in each channel. Moreover, our scheme can be extended to an N-mechanical-mode EOM system, in which N discrete channels will be observed and controlled. This study opens up prospects for quantum information transduction and storage with a wide bandwidth and multichannel quantum interface.

Hybrid coupling optomechanical assisted nonreciprocal photon blockade

The properties of the open quantum system in quantum information is a science now extensively investigated more generally as a fundamental issue for a variety of applications. Usually, the states of the open quantum system might be disturbed by decoherence which will reduce the fidelity in the quantum information processing. So it is better to eliminate the influence of the environment. However, as part of the composite system, rational use of the environment system could be beneficial to quantum information processing. Here we theoretically studied the environment induced quantum nonlinearity and energy spectrum tuning method in the optomechanical system. And we found that the dissipation coupling of the hybrid dissipation and dispersion optomechanical system can induce the coupling between the environment and system in the cross-Kerr interaction form. When the symmetry is broken with a directional auxiliary field, the system exhibits the non-reciprocal behavior during the photon excitation and photon blockade for the clockwise and counterclockwise modes of the whispering gallery mode microcavity. Furthermore, we believe that the cross-Kerr coupling can be more widely used in quantum information processing and quantum simulation.

Large and robust mechanical squeezing of optomechanical systems in a highly unresolved sideband regime via Duffing nonlinearity and intracavity squeezed light

We propose a scheme to generate strong and robust mechanical squeezing in an optomechanical system in the highly unresolved sideband (HURSB) regime with the help of the Duffing nonlinearity and intracavity squeezed light. The system is formed by a standard optomechanical system with the Duffing nonlinearity (mechanical nonlinearity) and a second-order nonlinear medium (optical nonlinearity). In the resolved sideband regime, the second-order nonlinear medium may play a destructive role in the generation of mechanical squeezing. However, it can significantly increase the mechanical squeezing (larger than 3dB) in the HURSB regime when the parameters are chosen appropriately. Finally, we show the mechanical squeezing is robust against the thermal fluctuations of the mechanical resonator. The generation of large and robust mechanical squeezing in the HURSB regime is a combined effect of the mechanical and optical nonlinearities.

Converting microwave and telecom photons with a silicon photonic nanomechanical interface

Practical quantum networks require low-loss and noise-resilient optical interconnects as well as non-Gaussian resources for entanglement distillation and distributed quantum computation. The latter could be provided by superconducting circuits but existing solutions to interface the microwave and optical domains lack either scalability or efficiency, and in most cases the conversion noise is not known. In this work we utilize the unique opportunities of silicon photonics, cavity optomechanics and superconducting circuits to demonstrate a fully integrated, coherent transducer interfacing the microwave X and the telecom S bands with a total (internal) bidirectional transduction efficiency of 1.2% (135%) at millikelvin temperatures. The coupling relies solely on the radiation pressure interaction mediated by the femtometer-scale motion of two silicon nanobeams reaching a Vπ as low as 16 μV for sub-nanowatt pump powers. Without the associated optomechanical gain, we achieve a total (internal) pure conversion efficiency of up to 0.019% (1.6%), relevant for future noise-free operation on this qubit-compatible platform.