Dissipation and amplification in quantum optics

Haozhen Li, Ran Zeng, Miao Hu +5 more

Abstract Optical nonreciprocal transmission with unidirectional amplification in a gain-assisted cavity-QED system is investigated. The results demonstrate that unidirectional amplification of this system is induced by the phase difference between the atom–cavity coupling strengths associated with the optical gain and a phase-controlled unidirectional amplifier can be achieved. The optimal parameter conditions for the observation of ideal unidirectional amplification are obtained analytically, and are shown to be dependent on phase, atom–cavity and cavity–cavity coupling strength, and atomic dissipation. In particular, it is found that atomic dissipation is another essential condition for the realization of nonreciprocal amplification other than breaking of the time-reversal symmetry, and our unidirectional amplifier is robust against atom–cavity coupling mismatch. Such unidirectional amplifiers are crucial nonreciprocal devices for controlling photon transmission and may have potential applications in quantum information processing.

Cong-Hua Yan, W. Z. Jia, Xin-Hong Jia +3 more

Dissipations in the waveguide-cavity systems destroy quantum interference between the incident signal photons and the cavity photons linearly and, thus, usually limit the manipulation of the photon transport. Here, we adopt a four-mode microring cavity including both second-order (${\ensuremath{\chi}}^{(2)}$) and third-order (${\ensuremath{\chi}}^{(3)}$) nonlinearities side coupled to two different waveguides to manipulate photon transport against dissipative effects. The results show that the incident signal photons can be amplified due to the optical parametric amplification (OPA) originated from ${\ensuremath{\chi}}^{(3)}$ nonlinearities. Owing to the coherent interference between cavity photons with different frequencies, the transmission spectra of the signal field are split into two amplified peaks. The transmission intensities are not always linearly reduced by increasing the dissipations but determined by the competition between the OPA and the dissipations. It means that we can utilize the OPA process to overcome the dissipative effects to manipulate photon transport and, thus, control the transmission intensities of the incident signal photon from ${T}_{c}=0$ to ${T}_{c}>100%$. This competition can also be used to convert the signal field to the idler field with amplified efficiencies.

R. Loudon

H. C. Fan, Liyun Hu

Yun-Ru Fan, Yong Geng, Ji Liu +9 more

Dissipative Kerr solitons in optical microresonators underpin chip-scale frequency combs with applications ranging from coherent telecommunications to precision spectroscopy. Yet the characterization of their intrinsic femtosecond temporal structure remains challenging, as the low pulse energy and broad spectral bandwidth necessitate optical amplification and careful dispersion compensation in conventional ultrafast diagnostics, both of which can significantly distort the waveform. Here we demonstrate a quantum-interference metrology of microcomb solitons based on Hong-Ou-Mandel interference. By attenuating the soliton stream to the single-photon level and measuring fourth-order interference, we directly retrieve near transform-limited pulse durations without amplification or dispersion management, remaining accurate even after propagation through 25 km of standard fiber. The same interferogram also provides direct access to the temporal separations in multi-soliton states by converting inter-soliton separations into additional interference dips at corresponding delays, enabling sub-picosecond characterization of their intracavity temporal structure. This quantum-inspired paradigm introduces a fundamentally new metrological approach that is immune to amplification and dispersion distortions, offering a powerful tool for the characterization of complex soliton physics.