分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要： Quantum Langevin noise makes experimental realization of genuine quantum-optical parity-time (PT) symmetry in a gain-loss-coupled open system elusive. Here, we challenge this puzzle by exploiting twin beams produced from a nonlinear parametric process, one undergoing phase-sensitive linear quantum amplification (PSA) and the other engaging balanced loss merely. Unlike all previous studies involving phase-insensitive amplification (PIA), our PSA-loss scheme allows one quadrature pair to experience PT symmetry, a unique quantum effect without any classical counterpart. Such symmetry showcases many radical noise behaviors beyond conventional quantum squeezing and inaccessible to any PIA-based platform. Importantly, it is the only non-Hermitian system hitherto that enables the emergence of non-Hermiticity-induced quantum-to-classical transition for the same quantum observable when crossing exceptional point. Utilizing this quadrature-PT structure, we have further studied its potential in quantum sensing by exploring the quantum Cram\'er-Rao bound or Fisher information. Besides, the proposed quadrature PT symmetry also sheds new light on protecting continuous-variable (CV) qubits from decoherence in lossy transmission, a long-standing conundrum for various CV-based quantum technologies.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
Kunpeng Jia
Xinwei Yi
Xiaohan Wang
Yunfeng Liu
Shu-Wei Huang
Xiaoshun Jiang
Wei Liang
Zhenda Xie
Shi-ning Zhu
摘要： Microresonator-based optical frequency comb (microcomb) has the potential to revolutionize the accuracy of frequency synthesizer in radar and communication applications. However, fundamental limit exists for low noise microcomb generation, especially in low size, weight, power and cost (SWaP-C) package. Here we resolve this limit, by the demonstration of an automated turnkey microcomb, operating close to its low quantum-limited phase noise, within a compact setup size of 85 mm * 90 mm * 25 mm. High quality factor fiber Fabry-Perot resonator (FFPR), with Q up to 4.0 * 10^9, is the key for both low quantum noise and pump noise limit, in the diode-pump case in a self-injection locking scheme. Low phase noise of -80 and -105 dBc/Hz at 100 Hz, -106 and -125 dBc/Hz at 1 kHz, -133 and -148 dBc/Hz at 10 kHz is achieved at 10.1 GHz and 1.7 GHz repetition frequencies, respectively. With the simultaneous automated turnkey, low-noise and direct-diode-pump capability, our microcomb is ready to be used as a low-noise frequency synthesizer with low SWaP-C and thus field deployability.
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