Channel multiplexing quantum communication based on exploiting continuous-variable entanglement of optical modes offers great potential to enhance channel capacity and save quantum resource. Here, we present a frequency-comb-type control scheme for simultaneously extracting a lot of entangled sideband modes with arbitrary frequency detuning from a squeezed state of light. We experimentally demonstrate fourfold channel multiplexing quantum dense coding communication by exploiting the extracted four pairs of entangled sideband modes. Due to high entanglement and wide frequency separation between each entangled pairs, these quantum channels have large channel capacity and the cross talking effect can be avoided. The achieved channel capacities have surpassed that of all classical and quantum communication under the same bandwidth published so far. The presented scheme can be extended to more channels if more entangled sideband modes are extracted.

The light-matter quantum interface that can create quantum correlations or entanglement between a photon and one atomic collective excitation is a fundamental building block for a quantum repeater. The intrinsic limit is that the probability of preparing such nonclassical atom-photon correlations has to be kept low in order to suppress multiexcitation. To enhance this probability without introducing multiexcitation errors, a promising scheme is to apply multimode memories to the interface. Significant progress has been made in temporal, spectral, and spatial multiplexing memories, but the enhanced probability for generating the entangled atom-photon pair has not been experimentally realized. Here, by using six spin-wave-photon entanglement sources, a switching network, and feedforward control, we build a multiplexed light-matter interface and then demonstrate a $\sim \text{sixfold}$ ($\sim \text{fourfold}$) probability increase in generating entangled atom-photon (photon-photon) pairs. The measured compositive Bell parameter for the multiplexed interface is $2.49\pm 0.03$ combined with a memory lifetime of up to $\sim 51\mu \mathrm{s}$.

We demonstrate the dependence of the squeezing and anti-squeezing factors on the seed beam power at different pump beam noise levels. The results indicate that a seed field injected into the optical parametric amplifier (OPA) dramatically degenerates the squeezing factor due to noise coupling between the pump and seed fields, even if both the pump and seed fields reach the shot noise limit. The squeezing and anti-squeezing factors are immune to the pump beam noise due to no noise coupling when the system operates for the generation of squeezed vacuum states. The squeezing factor degrades gradually as the pump beam intensity noise and seed beam power is increased. The influence of the two orthogonal quadrature variations is mutually independent of each other.

High-fidelity quantum teleportation is necessary to configure a cubic phase gate that enables the processing of the nonclassicality in an input quantum state. The noise variance of the antisqueezing component, which increases rapidly with a higher pump factor, contaminates the squeezing component due to the phase fluctuation and results in a reduction of the fidelity. Here, we balance the influence of the extraction loss and phase fluctuation on the fidelity and optimize the performance of quantum teleportation. As a result, a fidelity $F=0.905\pm 0.022$ is experimentally achieved. The ultrahigh fidelity is expected to configure a cubic phase gate involving four-time sequential teleportation to perform universal continuous-variable quantum information processing.

Squeezing transformation as an essential component of quantum information processing, gives rise to the possibility to perform various tasks such as distributed quantum computation and the quantum‐logic gate. However, the reported squeezing gate with best performance so far is realized with low success probability, while the performance of the deterministic ones is currently circumscribed by the limited squeezing degree of the nonclassical ancilla. To address this issue, a new scheme of deterministic and universal quantum squeezing gate with the property of nonlocal operation owing to the teleportation‐like protocol is developed and demonstrated. A high‐fidelity squeezing operation, even when the level of target squeezing being up to 10 dB, is demonstrated where a squeezed state with nonclassical noise reduction of 6.5 dB is directly observed. Moreover, a high‐fidelity complex operation including a Fourier transformation and a phase squeezing gate are performed, exploring the potential of implementing the complex task of quantum information processing with the presented functional unit. The method can be applied to distributed quantum processor, the creation of exotic nonclassical states, and quantum error correction.

We demonstrate the experimental detection of an optical squeezing covering several higher resonances of the optical parametric amplifier (OPA) by adopting a bichromatic local oscillator (BLO). The BLO is generated from a waveguide electro-optic phase modulator (WGM) and subsequent optical mode cleaner (OMC), without the need of additional power balance and phase control. The WGM is used for generating the frequency-shifted sideband beams with equal power and certain phase difference, and the OMC is used for filtering the unwanted optical modes. Among a measurement frequency range from 0 to 16.64 GHz, the maximum squeezing factors are superior to 10 dB below the shot noise limit for the first three discrete odd-order resonances of the OPA.