Speckled-speckle field as a resource for imaging techniques.

Correlated states of light, both classical and quantum, can find useful applications in the implementation of several imaging techniques. Among the employed sources, pseudo-thermal states, generated by the passage of a laser beam through a diffuser, represent the standard choice. To produce light with a higher level of correlation, in this work we consider and characterize the speckled-speckle field obtained with two diffusers using both a numerical simulation and an experimental implementation.

Efficient Implementation of Discrete-Time Quantum Walks on Quantum Computers.

Quantum walks have proven to be a universal model for quantum computation and to provide speed-up in certain quantum algorithms. The discrete-time quantum walk (DTQW) model, among others, is one of the most suitable candidates for circuit implementation due to its discrete nature. Current implementations, however, are usually characterized by quantum circuits of large size and depth, which leads to a higher computational cost and severely limits the number of time steps that can be reliably implemented on current quantum computers.

Generation of Pseudo-Random Quantum States on Actual Quantum Processors.

The generation of a large amount of entanglement is a necessary condition for a quantum computer to achieve quantum advantage. In this paper, we propose a method to efficiently generate pseudo-random quantum states, for which the degree of multipartite entanglement is nearly maximal. We argue that the method is optimal, and use it to benchmark actual superconducting (IBM's ) and ion trap (IonQ's ) quantum processors.

Correcting Coherent Errors by Random Operation on Actual Quantum Hardware.

Characterizing and mitigating errors in current noisy intermediate-scale devices is important to improve the performance of the next generation of quantum hardware. To investigate the importance of the different noise mechanisms affecting quantum computation, we performed a full quantum process tomography of single qubits in a real quantum processor in which echo experiments are implemented. In addition to the sources of error already included in the standard models, the obtained results show the dominant role of coherent errors, which we practically corrected by inserting random single-qubit unitaries in the quantum circuit, significantly increasing the circuit length over which quantum computations on actual quantum hardware produce reliable results.

Feasibility of a Novel Quantum Communication Protocol in Jerlov Type I Water.

Underwater communication based on the use of optical quantum resources has attracted a lot of attention in the last five years due to the potential advantages offered by quantum states of light. In this context, we propose to operate in the mesoscopic intensity regime, where the optical states are well populated and the employed detectors have photon-number resolution. By exploiting these features, we demonstrate that a novel communication protocol based on the experimental quantification of nonclassicality of mesoscopic twin-beam states can be used to transmit binary signals encoded in two single-mode pseudothermal states with different mean values through a Jerlov type I water channel.