We report on the first experimental realization of the controlled-not (cnot) quantum gate and entanglement for two individual atoms of different isotopes and demonstrate a negligible cross talk between two atom qubits. The experiment is based on a strong Rydberg blockade for ${}^{87}\mathrm{Rb}$ and ${}^{85}\mathrm{Rb}$ atoms confined in two single-atom optical traps separated by $3.8\mu \mathrm{m}$. The raw fidelities of the cnot gate and entanglement are $0.73\pm 0.01$ and $0.59\pm 0.03$, respectively, without any corrections for atom loss or trace loss. Our work has applications for simulations of many-body systems with multispecies interactions, for quantum computing, and for quantum metrology.

Practical application of quantum information requires distinguishing multipartite entanglement in a complete, nondestructive, and robust way. Here we explore the possibility to accomplish such a task using Rydberg atoms based on blockade effect and user-defined-passage-based geometric quantum logic gates. Our proposal focuses on distinguishing groups of many-body Greenberger-Horne-Zeilinger (GHZ) states and groups of cluster states, and for bipartite cases distinguishing Bell states, which are basic ingredients of quantum information processing. We validate our proposal by numerical results, showing complete and nondestructive accomplishment of distinguishing above multipartite entangled states and also robustness against decoherence. We exemplify two practical applications regarding quantum teleportation and quantum dense coding to demonstrate the value of our proposal. This idea is scalable and experimentally relevant and can be readily generalized to other quantum information candidates, such as superconducting circuits, NV centers, as well as trapped-ion systems with different-level structures.

We show that the higher-order soliton evolution can be considerably affected by the relative positions of the zero-nonlinearity wavelength (ZNW) and zero-dispersion wavelength (ZDW) with respect to the input wavelength in photonic crystal fibers (PCFs) with frequency-dependent Kerr nonlinearity. By regulating the magnitude of nonlinear dispersion, the position of the ZNW and the strength of the doping Kerr nonlinearity can vary to a large extent, which significantly changes the general process of higher-order soliton evolution in the PCFs. Particularly, some interesting phenomena observed numerically in the PCFs with one ZDW and one ZNW are as follows: the formation of a blueshifted fundamental soliton that satisfies the phase-matching and group-velocity-matching conditions with a redshifted fundamental soliton, the tunneling effect of a fundamental soliton that transfers from one solitonic region to another one through a spectrally limited nonsolitonic region, and the generation of the high-intensity blueshifted dispersive wave and redshifted dispersive wave.

We demonstrate a method to simultaneously suppress the linewidths and stabilize the long-term frequency drifts of both 780-nm and 960-nm lasers to the 10-kHz level. We first use an iodine frequency stabilization laser as a frequency reference to stabilize the length of a tunable high-finesse transfer cavity (THFTC). Then two slave lasers of 780 nm and 960 nm are locked to this THFTC. In this way, the linewidths of slave lasers are suppressed to the order of 10 kHz, which are measured by delayed self-heterodyne measurements. Meanwhile, the long-term frequency drifts are stabilized to be less than 22 kHz for 10 h. With the locked lasers, we realize the coherent Rydberg excitation of a single ${}^{87}\mathrm{Rb}$ atom and keep the exciting stable and repeatable for 10 h, which is essential for Rydberg-mediated single-atom quantum information processing. This dual-laser frequency stabilization and transfer method can also be used in other high-resolution experiments in atomic physics, precision metrology, and molecular spectroscopy.

This article presents a diamond nitrogen-vacancy (NV) center-based magnetic field sensor using a voltage-controlled oscillator (VCO) integrated with a filtering antenna. In existing NV-based quantum sensing systems, microwave source and delivery units are implemented by a set of bulky and costly instruments. This limits its practical applications as well as portability. Here, a VCO integrated with the filtering antenna is designed, providing a more uniform, efficient, broadband and lower phase noise microwave field coupling to the NV centers. As a result, the sensitivity and the dynamic range have been improved over the conventional scheme using separate microwave components, such as antennas, transmission lines, and resonators. Moreover, in this work, the optic filter and photodetector are also integrated using the hybrid microwave integrated circuits (HMICs) technique for the first time. This significantly increases the integration level and reduces the cost of the NV-based magnetometers. The experimental results indicate that our VCO integrated filtering antenna achieves a sensitivity of $8.52~\mu \text{T}$ /Hz $^{\mathrm {1/2}}$ and a dynamic range up to 32.73 dB, which are both greatly improved compared to the VCO with a single resonator. This validates the effectiveness of the approach.