Advanced quantum technologies最新文献

Photocurrents in wide bandgap materials provide valuable insights into the dynamics of intrinsic defects. In article number 2400237, Ralf Wunderlich and co-workers use a commercially available charge integrator IC with switchable input on a printed circuit board (cover image) for low-noise current measurements with a resolution of about 100 fA. Thus, the authors can image and detect small numbers of individual defects in ultrapure diamond. Furthermore, the authors conduct photocurrent-detected magnetic resonance (PDMR) on NV centers. The work paves the way for low-cost, miniaturized, simple and time-resolved photocurrent measurements of solid-state defects.

Zero noise extrapolation (ZNE) is a method that amplifies and extrapolates noise to a noise-free point. The cover image shows a modified method called purity-assisted ZNE (pZNE). This method enhances the effectiveness of ZNE by accumulating the noises with the forward and backward evolutions to extrapolate the ideal expectation from noisy expectations along the purity of the noisy output state to the ideal pure state. For further details, see article number 2400150 by Kai Xu, Heng Fan, and co-workers.

This cover image is the 3D rendering of a quantum photonic device concept consisting of a whispering gallery mode microlaser coupled to a ridge waveguide. Such a device could potentially be used to resonantly excite a single-photon emitter that is subsequently integrated into a ridge waveguide. This allows for on-chip and on-demand generation of single photons in the context of integrated quantum photonic circuits. In article number 2400195, Stephan Reitzenstein and co-workers use finite element simulations to investigate the resonance quality of the cavity and its coupling efficiency.

A quantum polarimetry method using entangled photons to improve measurement precision is introduced in article number 2400059 by Ali Pedram, Vira R. Besaga, Frank Setzpfandt, and Özgür E. Müstecaplıoğlu. By calculating precision bounds and estimating the rotation angle of optical elements, both theoretically and experimentally, it is shown that the capability of entanglement to enhance accuracy is diminished with noise. Experimental noise induces bias in estimators, reducing accuracy and precision depending on chosen estimators and noise channels.

The cover image depicts coupling of the light emission of single quantum emitters to single mode fibers. 3D printed microoptics are used to create the aspheric optics that matches the numerical apertures of light emission cone and fibers to each other. Additionally, a 3D printed chuck is used to place the fiber in the correct distance and with the correct horizontal alignment over the quantum emitters. The article by Harald Giessen and co-workers (article number 2400135) describes the quantification of the alignment accuracy and reproducibility of such 3D printed couplers. [Cover image: © Florian Sterl, Sterltech Optics.]

In article number 2400149, Arindam Dutta and co-workers study the implementation of high-dimensional quantum key distribution protocols, HD-Ext-B92 and HD-BB84, via satellite. The study modifies key rate calculations to explore variations in key rate, probability distribution, and quantum bit error rate (QBER) with respect to dimension and noise. The research examines how the average key rate changes with zenith angle and link length under different weather conditions, showing HD-BB84's superior performance in higher dimensions despite higher QBER saturation. The down-link configuration is shown to be preferable over the up-link configuration.

Chiral interaction between light and quantum emitters leads to emergence development of chiral quantum optics and stimulates a wide range of practical applications in quantum regime, such as single-photon isolation and photon unidirectional emission. Cavity optomechanics studying the interaction between optical and mechanical resonators plays an important role in the field of quantum optics. However, how to achieve the chiral interaction between light and mechanical oscillators and explore the applications of the chiral optomechanical systems are still difficult encountered in cavity optomechanics. Here, a method is proposed to achieve chiral optomechanical interaction by exploiting directional squeezed light in a multimode optomechanical system. Based on the chiral interaction between photon and phonon, the nonreciprocal photon transport at a single-photon level can be realized. An isolation ratio of $��>�40��\text{dB}�$ and a negligible insertion loss for the photonic isolator are obtained. This method paves the way to realize chiral optomechanical interaction for conducting chiral optomechanics and opens up the prospect of exploring and utilizing chiral photon–phonon manipulation in the quantum regime.

Inferring a quantum system from incomplete information is a common problem in many aspects of quantum information science and applications, where the principle of maximum entropy (MaxEnt) plays an important role. The quantum state compatibility problem asks whether there exists a density matrix $�\rho$ compatible with some given measurement results. Such a compatibility problem can be naturally formulated as a semidefinite programming (SDP), which searches directly for the existence of a $�\rho$. However, for large system dimensions, it is hard to represent $�\rho$ directly, since it requires too many parameters. In this work, MaxEnt is applied to solve various quantum state compatibility problems, including the quantum marginal problem. An immediate advantage of the MaxEnt method is that it only needs to represent $�\rho$ via a relatively small number of parameters, which is exactly the number of the operators measured. Furthermore, in case of incompatible measurement results, the method will further return a witness that is a supporting hyperplane of the compatible set. The method has a clear geometric meaning and can be computed effectively with hybrid quantum-classical algorithms.