Scalable quantum memory in the ultrastrong coupling regime

Circuit quantum electrodynamics, consisting of superconducting artificial atoms coupled to on-chip resonators, represents a prime candidate to implement the scalable quantum computing architecture because of the presence of good tunability and controllability. Furthermore, recent advances have pushed the technology towards the ultrastrong coupling regime of light-matter interaction, where the qubit-resonator coupling strength reaches a considerable fraction of the resonator frequency. Here, we propose a qubit-resonator system operating in that regime, as a quantum memory device and study the storage and retrieval of quantum information in and from the Z2 parity-protected quantum memory, within experimentally feasible schemes. We are also convinced that our proposal might pave a way to realize a scalable quantum random-access memory due to its fast storage and readout performances.Comment: We have updated the title, abstract and included a new section on the open-system dynamic

Dynamical Casimir effect entangles artificial atoms

We show that the physics underlying the dynamical Casimir effect may generate multipartite quantum correlations. To achieve it, we propose a circuit quantum electrodynamics (cQED) scenario involving superconducting quantum interference devices (SQUIDs), cavities, and superconducting qubits, also called artificial atoms. Our results predict the generation of highly entangled states for two and three superconducting qubits in different geometric configurations with realistic parameters. This proposal paves the way for a scalable method of multipartite entanglement generation in cavity networks through dynamical Casimir physics.Comment: Improved version and references added. Accepted for publication in Physical Review Letter

The quantum Rabi model in a superfluid Bose-Einstein condensate

We propose a quantum simulation of the quantum Rabi model in an atomic quantum dot, which is a single atom in a tight optical trap coupled to the quasiparticle modes of a superfluid Bose-Einstein condensate. This widely tunable setup allows to simulate the ultrastrong coupling regime of light-matter interaction in a system which enjoys an amenable characteristic timescale, paving the way for an experimental analysis of the transition between the Jaynes-Cummings and the quantum Rabi dynamics using cold-atom systems. Our scheme can be naturally extended to simulate multi-qubit quantum Rabi models. In particular, we discuss the appearance of effective two-qubit interactions due to phononic exchange, among other features.Comment: Improved version and references adde

A ROS/Gazebo-based framework for simulation and control of on-orbit robotic systems

The use of simulation tools such as ROS/Gazebo is currently common practice for testing and developing control algorithms for typical ground-based robotic systems but still is not commonly accepted within the space community. Numerous studies in this field use ad-hoc built, but not standardized, not open-source, and, sometimes, not verified tools that complicate, rather than promote, the development and realization of versatile robotic systems and algorithms for space robotics. This paper proposes an open-source solution for space robotics simulations called OnOrbitROS. This paper presents a description of the architecture, the different software modules, and the simulation possibilities of OnOrbitROS. It shows the key features of the developed tool, with a particular focus on the customization of the simulations and eventual possibilities of further expansion of the tool. In order to show these capabilities, a computed torque-based controller for the guidance of a free-floating manipulator is proposed and simulated using the ROS/Gazebo-based framework described in the paper

Collective Identity and Voice at the Australian Citizens' Parliament

This paper examines the role of collective identity and collective voice in political life. We argue that persons have an underlying predisposition to use collective dimensions, such as common identities and a public voice, in thinking and expressing themselves politically. This collective orientation, however, can be either fostered or weakened by citizens’ political experiences. Although the collective level is an important dimension in contemporary politics, conventional democratic practices do not foster it. Deliberative democracy is suggested as an environment that might allow more ground for citizens to express themselves not only in individual but also in collective terms. We examine this theoretical perspective through a case study of the Australian Citizens’ Parliament, in which transcripts are analyzed to determine the extent to which collective identities and common voice surfaced in actual discourse. We analyze the dynamics involved in the advent of collective dimensions in the deliberative process and highlight the factors—deliberation, nature of the discussion, and exceptional opportunity—that potentially facilitated the rise of group identities and common voice. In spite of the strong individualistic character of the Australian cultural identity, we nonetheless found evidence of collective identity and voice at the Citizens’ Parliament, expressed in terms of national, state, and community levels. In the conclusion, we discuss the implications of those findings for future research and practice of public deliberation

Critical Quantum Metrology with a Finite-Component Quantum Phase Transition

Physical systems close to a quantum phase transition exhibit a divergent susceptibility, suggesting that an arbitrarily high precision may be achieved by exploiting quantum critical systems as probes to estimate a physical parameter. However, such an improvement in sensitivity is counterbalanced by the closing of the energy gap, which implies a critical slowing down and an inevitable growth of the protocol duration. Here, we design different metrological protocols that exploit the superradiant phase transition of the quantum Rabi model, a finite-component system composed of a single two-level atom interacting with a single bosonic mode. We show that, in spite of the critical slowing down, critical quantum optical probes can achieve a quantum-enhanced time scaling of the sensitivity in frequency-estimation protocols

Path generation and control of humanoid robots during extravehicular activities

This paper proposes and investigates strategies that can be used to plan the motion and control of humanoid robots in some elementary tasks that characterize extravehicular activities. The humanoid robot taken into account is a torso with two arms and two grippers at their extremities. This study addresses the problem of robot motion on the complex system of handrails and handles that characterize the International Space Station. Such a complex task has been divided into two elementary sub-tasks: motion planning and tracking the planned trajectories. First, an optimization procedure is presented to plan and coordinate the robot's arms motions and graspers to achieve the desired location using handrails. Then, a low-level controller is used to guarantee that the robots' actuators can follow these previously generated trajectories. Simulation results assess the applicability of the proposed strategy in different typical operations that potentially can be performed in an extravehicular activity scenario

Directional Receivers for Diffusion-Based Molecular Communications

The particle motion in diffusion-based molecular communication systems is typically modeled by using Brownian processes. In particular, this model is used to characterize the propagation of signal molecules after their release from the transmitter. This motion cannot include directionality in the propagating signal and translates into omnidirectional broadcast communications. In order to make such molecular communications system suitable for supporting communications protocols at the molecular scales, we propose to improve the receiver capabilities by introducing a form of directionality while receiving biological signals. Inspired by the directionality introduced in electromagnetic communications by means of directional antennas, we designed a nanomachine receiver having directionality properties. Our aim is to increase the average concentration of signal molecules, also referred to as carriers, in the area around the receiver surface. In this way, it is possible to increase the signal strength at the receiver. For this purpose, we propose to use a purely reflecting shell to be placed at a configurable distance from the receiver surface. The shape of the shell can be modeled as either a spherical cap or a cylinder with an empty basis. The presence of this surface causes a number of signal molecules to remain trapped in a region close to the receiver surface for a sufficiently long time. In this way, the probability of assimilating additional carriers by the compliant receptors present on the receiver surface increases. By means of an extensive simulation campaign, we identified the most suitable configuration able to provide a significant advantage with respect to those not adopting the proposed solution. The resulting approach can be regarded as an enabler of protocols for diffusive molecular communications taking advantage of directionality properties at the receiver site. It can result in an increased communication range or in improved capabilities of discriminating signals of coexisting molecular communication systems