We demonstrate a platform for generating bipartite entangled quantum frequency combs using magnesium fluoride microdisk resonators with high Q factors. The system supports 14 continuous-variable quantum modes, with the frequency-dependent squeezing state being finely adjustable.
Integrated Kerr quantum frequency combs (QFCs), with the potential to generate multiple and scalable quantum states, have emerged as a compact, stable, and fundamental resource for broadband entanglement. Here, we build a platform for designing bipartite entangled QFCs via an on-chip silicon nitride microring resonator. By establishing the system quantum dynamics of Kerr nonlinear microresonators, our platform can support up to 12 continuous-variable quantum modes, in the form of six simultaneously two-mode squeezed pairs under the influence of hysteresis. The entanglement degree of frequency-mode pairs is dependent on the resonator structure and ambient temperature. By adjusting the cavity temperature, we can optimize the performance of entanglement under certain injected pump power and pump detuning. Our comprehensive QFC designing process and entanglement distribution control may ameliorate the generation and optimization of entanglement.
Abstract Considerable efforts have been devoted to augmenting the performance of displacement sensors constrained by quantum noise, particularly within high‐precision applications such as gravitational wave detection. Frequency‐dependent squeezing methodologies have adeptly exceeded the standard quantum limit in optomechanical force measurements, catalyzing profound advancements in the field. Concurrently, notable strides in integrated photonics have paved the way for the realization of integrated Kerr quantum frequency combs (QFCs). In this work, a sophisticated platform designed for the creation of Einstein–Podolsky–Rosen (EPR)‐entangled QFCs utilizing on‐chip silicon nitride microring resonators is presented. This platform facilitates an exhaustive analysis and optimization of entanglement performance, establishing a robust framework for noise mitigation. By incorporating the quantum dynamics of Kerr nonlinear microresonators, the system accommodates at least 12 continuous‐variable quantum modes, including 6 pairs of concurrently EPR‐entangled states. Moreover, through precise tuning of the detection angle of the idler mode, the signal mode transitions into a single‐mode squeezed state. Harnessing the frequency‐dependent nature of this detection angle enables the achievement of frequency‐dependent squeezing. A comparative analysis under different dispersion conditions is also presented.
Frequency-dependent squeezing (FDS) represents a well established way to address quantum noise (QN) in Gravitational-Wave (GW) Earth-based detectors, such as LIGO, Virgo, and KAGRA. This technique is realized with the use of an external detuned optical resonator, the filter cavity. The experiment we present here is a table-top prototype that will probe a cheaper, more compact and more flexible strategy for broadband QN reduction (Ma et al., 2017). This scheme is based on two-mode Einstein–Podolsky–Rosen (EPR) entangled squeezed light, and it works without any filter cavity. The EPR-entangled beams will propagate in a small-scale suspended interferometer with high-finesse arm-cavities. This experiment aims at validating the EPR conditional squeezing at audio frequencies, suited for GW detection, implementing also innovative optical techniques.
The optical microresonator-based frequency comb (microcomb) provides a versatile platform for nonlinear physics studies and has wide applications ranging from metrology to spectroscopy. The deterministic quantum regime is an unexplored aspect of microcombs, in which unconditional entanglements among hundreds of equidistant frequency modes can serve as critical ingredients to scalable universal quantum computing and quantum networking. Here, we demonstrate a deterministic quantum microcomb in a silica microresonator on a silicon chip. 40 continuous-variable quantum modes, in the form of 20 simultaneously two-mode squeezed comb pairs, are observed within 1 THz optical span at telecommunication wavelengths. A maximum raw squeezing of 1.6 dB is attained. A high-resolution spectroscopy measurement is developed to characterize the frequency equidistance of quantum microcombs. Our demonstration offers the possibility to leverage deterministically generated, frequency multiplexed quantum states and integrated photonics to open up new avenues in fields of spectroscopy, quantum metrology, and scalable, continuous-variable-based quantum information processing.
Future gravitational-wave detectors will use frequency-dependent squeezed vacuum states to obtain broadband reduction of quantum noise. Quantum noise is one of the major limitations to the sensitivity of these detectors. Advanced LIGO+, Advanced Virgo+, and KAGRA plan to generate frequency-dependent squeezed states by coupling a frequency-independent squeezed light state with a filter cavity. An alternative technique is under consideration, based on conditional squeezing with quantum entanglement: Einstein–Podolsky–Rosen (EPR) squeezing. In the EPR scheme, two vacuum entangled states, the signal field at ω 0 and the idler field at ω 0 + Δ , must be spatially separated with an optical resonator and sent to two separate homodyne detectors. In this framework, we have designed and tested a solid Fabry–Perot etalon, to be used in an EPR table-top experiment prototype, thermally controlled without the use of a control probe optical beam. This device can also be used in optical experiments where the use of a bright beam to control an optical resonator is not possible, or where a simpler optical device is preferred.