Search results for "W state"

Strong monogamy of bipartite and genuine multipartite entanglement: The Gaussian case

2007

We demonstrate the existence of general constraints on distributed quantum correlations, which impose a trade-off on bipartite and multipartite entanglement at once. For all N-mode Gaussian states under permutation invariance, we establish exactly a monogamy inequality, stronger than the traditional one, that by recursion defines a proper measure of genuine N-partite entanglement. Strong monogamy holds as well for subsystems of arbitrary size, and the emerging multipartite entanglement measure is found to be scale invariant. We unveil its operational connection with the optimal fidelity of continuous variable teleportation networks.

Sensitivity of external resources to cash flow under financial constraints

2014

Abstract This paper explores the external financing–cash flow relationship in capital structure theory by comparing unlisted (financially constrained) and listed (financially unconstrained) companies. We postulate that investment is determined endogenously in the case of unlisted firms, as they are strongly dependent on internally generated funds (cash flow). Consequently, unlisted firms invest their cash flow in profitable projects, using any residual cash flow to increase their holdings of safe assets. In turn, listed companies determine their investment exogenously and may reduce leverage if they raise an excess of cash flow. As a result, listed companies would react more negatively to s…

Make Fitness Fun: Could Novelty Be the Key Determinant for Physical Activity Adherence?

2020

The benefits of physical activity (PA) are well known and are extensively delineated in the scientific literature. Regular participation in PA, or exercise as its subset (structured, preplanned form of PA), is positively associated with numerous physical and psychological health benefits across all population subgroups (i.e., different age groups, gender, ethnicity, and socioeconomic status) (Paterson and Warburton, 2010; Warburton and Bredin, 2017). The current PA guidelines for adults, proposed by the American College for Sports Medicine and American Heart Association (ACSM/AHA), recommend the accumulation of at least 150 min of moderate intensity aerobic PA per week (Nelson et al., 2007)…

Entangling two uncoupled flux qubits via their sequential interaction with a quantized electromagnetic field

2005

A theoretical scheme for the generation of maximally entangled states of two superconducting flux qubits via their sequential interaction with a monochromatic quantum field is presented. The coupling of the qubits with the quantized field can be tuned on and off resonance by modulating the effective Josephson energy of each qubit via an externally applied magnetic flux. The system operates in such a way as to transfer the entanglement from a bipartite field-qubit subsystem to the two qubits. This scheme is attractive in view of the implementation of practical quantum processing systems.

Dynamical entanglement-transfer for quantum information networks

2004

A key element in the architecture of a quantum information processing network is a reliable physical interface between fields and qubits. We study a process of entanglement transfer engineering, where two remote qubits respectively interact with entangled two-mode continuous variable (CV) field. We quantify the entanglement induced in the qubit state at the expenses of the loss of entanglement in the CV system. We discuss the range of mixed entangled states which can be obtained with this set-up. Furthermore, we suggest a protocol to determine the residual entangling power of the light fields, inferring, thus, the entanglement left in the field modes which, after the interaction, are no lon…

Maximally entangled states of two flux qubits in a microwave cavity

2005

Dissipative effects on a generation scheme of a W state in an array of coupled Josephson junctions

2011

The dynamics of an open quantum system, consisting of three superconducting qubits interacting with independent reservoirs, is investigated to elucidate the effects of the environment on a unitary generation scheme of W states (Migliore R et al 2006 Phys. Rev. B 74 104503). To this end a microscopic master equation is constructed and its exact resolution predicts the generation of a Werner-like state instead of the W state. A comparison between our model and a more intuitive phenomenological model is also considered, in order to find the limits of the latter approach in the case of structured reservoirs.

GENERATION OF ENTANGLED STATES OF TWO DISTANT CAVITY MODES VIA JOSEPHSON JUNCTION BASED DEVICES

2007

We present a simple scheme for the preparation of entangled states of the e.m. modes of two spatially separated microwave cavities exploiting their interaction with two superconducting SQUID rings embedded within them. The scheme requires that the two SQUID qubits are initially prepared in an entangled state and the possibility of controlling both the coupling strengths and the interaction times. We also briefly discuss the importance of such a theoretical scheme in view of possible applications in the context of quantum computing and its experimental feasibility.

Enhancing coherence in molecular spin qubits via atomic clock transitions

2016

Quantum computing is an emerging area within the information sciences revolving around the concept of quantum bits (qubits). A major obstacle is the extreme fragility of these qubits due to interactions with their environment that destroy their quantumness. This phenomenon, known as decoherence, is of fundamental interest1,2. There are many competing candidates for qubits, including superconducting circuits3, quantum optical cavities4, ultracold atoms5 and spin qubits6,7,8, and each has its strengths and weaknesses. When dealing with spin qubits, the strongest source of decoherence is the magnetic dipolar interaction9. To minimize it, spins are typically diluted in a diamagnetic matrix. For…

ERGODICITY IN RANDOMLY COLLIDING QUBITS

2009

The dynamics of a single qubit randomly colliding with an environment consisting of just two qubits is discussed. It is shown that the system reaches an equilibrium state which coincides with a pure random state of three qubits. Furthermore the time average and the ensemble averages of the quantities used to characterize the approach to equilibrium (purity and tangles) coincide, a signature of ergodic behavior.