We consider the problem of designing an optimal quantum detector with a fixed rate of inconclusive results that maximizes the probability of correct detection, when distinguishing between a collection of mixed quantum states. We show that the design of the optimal detector can be formulated as a semidefinite programming problem, and derive a set of necessary and sufficient conditions for an opt...

A strong entanglement monotone, which never increases under local operations and classical communications (LOCC), restricts quantum entanglement manipulation more strongly than the usual monotone since the usual one does not increase on average under LOCC. We propose new strong monotones in mixed-state entanglement manipulation under LOCC. These are related to the decomposability and 1-positivi...

This paper evaluates performance differences between government owned, mixed sector and private sector enterprises in India for the period 1973–1974 to 1988–1989. The results establish that enterprises owned by the central government and state governments are less efficient than mixed or private sector enterprises, while mixed sector enterprises are less efficient than those in the private sect...

It is shown that Uhlmann’s parallel transport of purifications along a path of mixed states represented by 2 × 2 density matrices is just the path ordered product of Thomas rotations. These rotations are invariant under hyperbolic translations inside the Bloch sphere that can be regarded as the Poincaré ball model of hyperbolic geometry. A general expression for the mixed state geometric phase ...

Entanglement purification protocols (EPP) and quantum errorcorrecting codes (QECC) provide two ways of protecting quantum states from interaction with the environment. In an EPP, perfectly entangled pure states are extracted, with some yield D, from a bipartite mixed state M ; with a QECC, an arbitrary quantum state |ξ〉 can be transmitted at some rate Q through a noisy channel χ without degrada...

Abstract: In several application fields like daily pluviometry data modelling, or motion analysis from image sequences, observations contain two components of different nature. A first part is made with discrete values accounting for some symbolic information and a second part records a continuous (real-valued) measurement. We call such type of observations “mixedstate observations”. This paper...

We show an improved ping − pong protocol which is based on the protocol showed by Kim Bostrom and Timo Felbinger [Phys. Rev. Lett. 89, 187902 (2002)]. We show that our protocol is asymptotically secure key distribution and quasisecure direct communication using a mixed state. This protocol can be carried out with great efficiency and speed with today’s technology, e.g. single photon source and ...

Quantum finite automata with mixed states are proved to be super-exponentially more concise rather than quantum finite automata with pure states. It was proved earlier by A. Ambainis and R. Freivalds that quantum finite automata with pure states can have an exponentially smaller number of states than deterministic finite automata recognizing the same language. There was an unpublished ‘‘folk th...

Geometric phase of an open quantum system that is interacting with a thermal environment (bath) is studied through some simple examples. The system is considered to be a simple spin-half particle which is weakly coupled to the bath. It is seen that even in this regime the geometric phase can vary with temperature. In addition, we also consider the system under an adiabatically time-varying magn...

We present a compared experimental investigation of the (a, b) plane vortex-state complex resistivity at 48 GHz in YBa2Cu3O7−δ, SmBa2Cu3O7−δ and Bi2Sr2CaCu2O8+x. In YBa2Cu3O7−δ and SmBa2Cu3O7−δ the field dependence of the response can be consistently described by a combination of flux flow and strong pair breaking due to the presence of lines of nodes in the gap. In Bi2Sr2CaCu2O8+x, by contrast...