Abstract The nonclassical states of light serve as potential candidates for emerging quantum information processes. A quantum information unit with higher information capacity is interesting and useful in large quantum information systems, such as quantum computations. The most mature way to increase information capacity is to employ a post‐selection or cascaded method with the biphoton state and polarizing beam splitters to increase the qubits of the entangled state. Another promising processing is shaping the temporal correlations of entangled state to high‐dimensional entangled states to increase the superposed states of each qubit. Based on the photon pair state in a hot atomic ensemble, experiments are conducted to shape its temporal correlations to multi‐periodic Rabi oscillations and nonlinear phase shifts. By employing the external dressing field to quantum transitions, the nonlinear interaction produces multiple frequency modes, shaping the temporal correlation of photon pairs to multi‐periodic Rabi oscillation and proposing a 3D energy–time‐entangled qubit for photon pair state. Interestingly, the maximum peak of the periodic Rabi oscillation can migrate with a longer correlation time because of a nonlinear phase shift. Wave shaping of the photon pair state, therefore, has the potential for applications in quantum information processes with higher information capacity and quantum memory.
Abstract The nonclassical states of light serve as potential candidates for emerging quantum information processes. A quantum information unit with higher information capacity is interesting and useful in large quantum information systems, such as quantum computations. The most mature way to increase information capacity is to employ a post‐selection or cascaded method with the biphoton state and polarizing beam splitters to increase the qubits of the entangled state. Another promising processing is shaping the temporal correlations of entangled state to high‐dimensional entangled states to increase the superposed states of each qubit. Based on the photon pair state in a hot atomic ensemble, experiments are conducted to shape its temporal correlations to multi‐periodic Rabi oscillations and nonlinear phase shifts. By employing the external dressing field to quantum transitions, the nonlinear interaction produces multiple frequency modes, shaping the temporal correlation of photon pairs to multi‐periodic Rabi oscillation and proposing a 3D energy–time‐entangled qubit for photon pair state. Interestingly, the maximum peak of the periodic Rabi oscillation can migrate with a longer correlation time because of a nonlinear phase shift. Wave shaping of the photon pair state, therefore, has the potential for applications in quantum information processes with higher information capacity and quantum memory.
Abstract The non‐classical states of light serve as a potential candidate for emerging quantum information process. A processing trend to enhance its scalability is to integrate multiple nonlinear processes with the dressed‐state picture into a single device, and therefore, are useful for quantum computations. Here, a novel method is proposed to experimentally achieve the generation of coexisting two pairs of narrow‐band biphotons by two four‐wave mixing processes in a single hot rubidium vapor cell. Based on the photon‐atom nonlinear interfaces, the generated biphotons exhibits genuine entanglement in time–energy. Meanwhile, the nonlinear susceptibility with the dressed‐state picture decides the temporal correlation of the biphotons wave packet as a damped periodic Rabi oscillation, suggesting the property of the high‐dimensional time–energy entangled state. Such a high‐dimensional entangled state also is an efficient way to enhance information carrying capacity. By alternating two nonlinear susceptibilities in a single device, respectively, there exists a competition of the generation rate between such two pairs of biphotons. Moreover, both generated two pairs of biphotons that violate the Cauchy–Schwarz inequality and show their non‐classical behavior.
The biphoton states have served as one of the candidates for most quantum‐enabled technologies. Moreover, with the benefit of photon–atom interactions, biphotons with controllable wave functions are particularly interesting in quantum information processes. Herein, an experimental realization of the shaping temporal correlation of biphotons from the four‐wave mixing process in a hot Rb atomic ensemble is presented. Based on the slow‐light effect and electromagnetically induced transparency in the group delay region, the precursor‐like propagation is observed and separated from the rising edge of the delayed wave packets of biphotons temporal correlation. In addition, the application of an additional dressing field enriches the features of the biphotons temporal correlation such as the manipulation of the dispersion experienced by the generated photons and controllable coherent time. Furthermore, with a higher optical depth and stronger dressing coupling effect, the temporal correlation of biphotons is shaped from the group delay region to the Rabi oscillation region and even superposed of them.
Abstract Nonclassical multiphoton have attracted extensive attention to serve as entangled resources for quantum information technology. Here, the continuous‐mode hyper‐entangled W‐class triphotons are theoretically generated through spontaneous six‐wave mixing (SSWM) in 85Rb. In nonlinear optical response, Zeeman sub‐states are high‐dimensionally quantized by polarized dressing. High‐dimensional entanglement is structured via atomic non‐Hermitian nature. Through linear optical response, the temporal correlations are shaped via diverse polarized dressing. SSWM‐based triphoton is a genuine triphoton possessing non‐Gaussian tripartite entanglement. The high production rate is due to co‐action of three strong input fields, electromagnetically induced transparency (EIT) protection, and slow light effect. Non‐Hermitian nature endows the system with sensitive adjustability around exceptional points (EP). Eventually, the results demonstrate multiple SSWMs causing oscillations with multiple periods in three‐photon temporal correlations for the nonlinear region, build a high‐dimensional three‐body entangled quantum network and transform multifarious profiles of the three‐photon temporal correlations for the linear region. Especially, both high‐dimensional and hyper entanglements are obtained, contributing to high quantum information capacity. Further, the system is switched among multiple states when non‐Hermitian nature is manipulated by polarized dressing. The research opens a broad prospect for generating the hyper‐entangled multiphoton with potential application in adjustable quantum networks of high information capacity.
We have theoretically analyzed nonclassical paired photons generated spontaneously from a four-level inverted-Y atomic system. We discuss the feasibility of biphoton generation due to different pumping arrangements. Two types of correlated photon pair emissions have been carefully examined: dressed cascade and dressed double-$\ensuremath{\Lambda}$ emissions. In the dressed cascade two-photon emission, the coincidence counting rate may exhibit a damped Rabi oscillation, in contrast with a simple exponential decay feature in the literatures. In the dressed double-$\ensuremath{\Lambda}$ configuration, we show that not only is the temporal correlation of entangled Stokes--anti-Stokes photons in agreement with discussions presented by Wen et al. [Phys. Rev. A 76, 013825 (2007)], but also the oscillation period may be manipulated by altering either the control Rabi frequency or the dressing Rabi frequency or both. All the observed damped Rabi oscillations in the two-photon coincidences result from the destructive interference among the possible four-wave mixing processes occurring in the atom-field interaction system. This feature of the two-photon amplitude is governed by the convolution between the phase matching and third-order nonlinear susceptibility. The methodology adopted here can be applied to other atomic-level configurations and provides a useful tool to study the spectroscopy of the system. The generated narrow-band photon pairs may have potential applications in long-distance quantum communication and quantum information processing.
Abstract The generation of a nonclassical multi-photon has aroused renewed interest in recent years. Here, we propose a new method to generate tri-photon and quad-photon correlations in time via a double-dressing spontaneous six-wave mixing and eight-wave mixing process in an atomic ensemble, respectively. When we only consider the nonlinear optical response, the coincidence counts of tri and quad photon serves as damped coherent Rabi oscillation. The coincident count of tri (quad) photon contains three (four) conditional two-photon correlation with 10 or 30 (26, 28 or 38) periods, corresponding to 11 or 19 (18 or 20) modes. These mode and periods of tri and quad photon result from destructive interference from the possible 4 or 8 six wave and 18 eight wave coherent channels, respectively. In addition, for tri-photon, the greater double-dressing field strength is, the fewer the number of periods are. The coherent times are also controlled by the double-dressing effect. Such results have potential applications in multi-mode quantum communication and quantum network.
Abstract The competition and coexistence between linear and nonlinear multiphoton optical responses in multidressing fields; these exhibit shaping temporal waveforms is investigated. In the group delay regime, the width of the rectangular profile in double‐dressing fields is reduced compared to that of the single‐dressing field. In the Rabi oscillation regime, the number of periods in double‐dressing fields increases relative to the single‐dressing field, and the tri‐ and quadphotons are observed to feature six and nine coherent channels, respectively. Finally, changing the optical depth and power of the dressing field can alter the optical response. Compared with the single‐dressing field, cascaded and nested double‐dressing fields reduce the linear coherence time and increase the number of periods; this is useful for photon storage and long‐distance communication. Moreover, increasing the number of dressing coherent channels increases the high‐dimensional entangled information capacity, which is more conducive to the realization of quantum communication and quantum networks.