Multimode quantum correlations and entanglements has drawn much attention recently due to its importance for both fundamental science and the future development of quantum information processing and quantum communication. Here, by using a four-wave mixing process with a conical pump beam and a conical probe beam, we experimentally generate the multimode quantum correlations between a conical probe beam and a conical conjugate beam, and we also observe about –2.6-dB intensity-difference squeezing between these two conical beams. In addition, we find the optimal value of each parameter in this scheme for further applications. Besides, the multi-spatial-mode nature of the generated quantum correlated beams is shown by comparing the variation tendencies of the intensity-difference noise of the probe and conjugate beams under global attenuation and local cutting attenuation. Our scheme may find potential applications in quantum information processing and quantum communication.
Multimode quantum correlations and entanglements has drawn much attention recently due to its importance for both fundamental science and the future development of quantum information processing and quantum communication. Here, by using a four-wave mixing process with a conical pump beam and a conical probe beam, we experimentally generate the multimode quantum correlations between a conical probe beam and a conical conjugate beam, and we also observe about –2.6-dB intensity-difference squeezing between these two conical beams. In addition, we find the optimal value of each parameter in this scheme for further applications. Besides, the multi-spatial-mode nature of the generated quantum correlated beams is shown by comparing the variation tendencies of the intensity-difference noise of the probe and conjugate beams under global attenuation and local cutting attenuation. Our scheme may find potential applications in quantum information processing and quantum communication.
Generation of multimode quantum states has drawn much attention recently due to its importance for both fundamental science and the future development of quantum technologies. Here, by using a four-wave mixing process with a conical pump beam, we have experimentally observed about -3.8 dB of intensity-difference squeezing between a single-axial probe beam and a conical conjugate beam. The multi-spatial-mode nature of the generated quantum-correlated beams has been shown by comparing the variation tendencies of the intensity-difference noise of the probe and conjugate beams under global attenuation and local cutting attenuation. Due to its compactness, phase-insensitive nature, and easy scalability, our scheme may find potential applications in quantum imaging, quantum information processing, and quantum metrology.
Extensive attention has been drawn in generating multimode quantum states in recent years. Many efforts have been made during the last decade to produce such states. In this paper, we have experimentally demonstrated a scheme for generating a multi-spatial-mode quantum light source by a non-degenerated four-wave mixing process with a conical pump and a conical probe in a hot atomic vapor cell. The degree of the intensity-difference squeezing between the generated twin beams is about −4.1 dB. Due to the similar conical shape of the concentric quantum correlated beams, both the amplified probe and the generated conjugate beams can be decomposed into many angular modes. We have also experimentally verified the multi-spatial-mode nature of the generated quantum correlation by comparing the noise levels' variation tendencies of global attenuation and local cutting attenuations. In addition, we have also found the optimal values of each parameter in this scheme for further applications. Due to our scheme's advantages such as compactness, phase-insensitivity, and easy scalability, we have already shown a promising candidate for generating multi-spatial-mode quantum states, which may find potential applications in quantum metrology and quantum imaging, such as quantum-enhanced superresolution and the generation of multiple quantum correlated images.
Multimode quantum states, such as multipartite quantum entanglement or quantum correlations, are important for both fundamental science and the future development of quantum technologies. Here we theoretically propose and experimentally realize a scheme that can fully exploit the multi-spatial-mode nature of the four-wave-mixing (FWM) process, i.e., spatial multiplexing, and thus integrates multiple FWM processes into a single cell at each stage of the cascaded process. The number of generated quantum-correlated beams 2n is exponentially dependent on the number of vapor cells n. In addition, the quantum correlations between the multiple beams also increase as the number of vapor cell increases. For the case of n=2, we experimentally show that the degree of intensity-difference squeezing between the four quantum-correlated beams in our scheme is enhanced to $\ensuremath{-}8.2\ifmmode\pm\else\textpm\fi{}0.2$ dB from $\ensuremath{-}5.6\ifmmode\pm\else\textpm\fi{}0.3$ and $\ensuremath{-}6.5\ifmmode\pm\else\textpm\fi{}0.2$ dB of squeezing obtained with a single FWM process. Our system may find applications in quantum information and precision measurement.
Phase-sensitive amplifiers (PSAs) have been widely studied in fiber amplifiers, with remarkable recent advances. They have also been implemented in an SU(1,1) interferometer. In this paper, we study an experimental scheme for the implementation of a two-mode PSA based on a four-wave mixing process in rubidium vapor. With the process seeded by coherent probe and conjugate beams, quantum correlation including intensity difference/sum squeezing and quadrature entanglement between the output probe and conjugate fields are theoretically analyzed. Compared to previous related research, several new and interesting results are reported here. The maximal degree of intensity difference squeezing can be enhanced by nearly 3 dB compared to a phase-insensitive amplifier with the same gain. It is also possible to generate intensity sum squeezing between the probe and conjugate fields by choosing the specific phase of the input beams. Moreover, quadrature entanglement between the probe and conjugate beams, which can be manipulated by the phase of the input beams, is predicted. Our scheme may find a variety of applications in quantum metrology and quantum information processing owing to its ability of quantum squeezing and entanglement manipulation.
Quantum correlations and entanglement shared among multiple quantum modes are important for both fundamental science and the future development of quantum technologies. This development will also require an efficient quantum interface between multimode quantum light sources and atomic ensembles, which makes it necessary to implement multimode quantum light sources that match the atomic transitions. Here, we report on such a source that provides a method for generating quantum correlated beams that can be extended to a large number of modes by using multiple four-wave mixing (FWM) processes in hot rubidium vapor. Experimentally, we show that two cascaded FWM processes produce strong quantum correlations between three bright beams but not between any two of them. In addition, the intensity-difference squeezing is enhanced with the cascaded system to -7.0±0.1 dB from the -5.5±0.1/-4.5±0.1 dB squeezing obtained with only one FWM process. One of the main advantages of our system is that as the number of quantum modes increases, so does the total degree of quantum correlations. The proposed method is also immune to phase instabilities due to its phase insensitive nature, can easily be extended to multiple modes, and has potential applications in the production of multiple quantum correlated images.
Multimode quantum resources or states, in which quantum correlations are shared and distributed among multiple parties, are important not only for fundamental tests of quantum effects but also for their numerous possible applications in quantum technologies, such as quantum imaging and quantum metrology. Here we demonstrate the single-step fabrication of a multimode quantum resource from four-wave mixing (FWM) process in hot Rb vapor using a spatially structured pump, which consists of a coherent combination of two tilted pump beams. During this FWM process, one probe beam is amplified, three conjugate and two new probe beams are generated. The measured degrees of the intensity squeezing for the four-beam case and six-beam case are around $\ensuremath{-}4.1\ifmmode\pm\else\textpm\fi{}0.1$ dB and $\ensuremath{-}4.7\ifmmode\pm\else\textpm\fi{}0.1$ dB, respectively. The generated multiple quantum correlated beams are naturally separated with distinct directions, which is crucial for sending them out to quantum nodes at different locations in quantum communication. Our scheme is compact, simple, phase insensitive, and easily scalable to larger number of quantum-correlated modes.