Balance between information gain and reversibility in weak measurement

We derive a tight bound between the quality of estimating a quantum state by measurement and the success probability of undoing the measurement in arbitrary dimensional systems, which completely describes the tradeoff relation between the information gain and reversibility. In this formulation, it is clearly shown that the information extracted from a weak measurement is erased through the reversing process. Our result broadens the information-theoretic perspective on quantum measurement as well as provides a standard tool to characterize weak measurements and reversals.Comment: 5 pages, final versio

Near-Complete Teleportation of a Superposed Coherent State

The four Bell-type entangled coherent states, |\alpha>|-\alpha> \pm |-\alpha> |\alpha> and |\alpha>|\alpha> \pm |-\alpha> |-\alpha>, can be discriminated with a high probability using only linear optical means, as long as |\alpha| is not too small. Based on this observation, we propose a simple scheme to almost completely teleport a superposed coherent state. The nonunitary transformation, that is required to complete the teleportation, can be achieved by embedding the receiver's field state in a larger Hilbert space consisting of the field and a single atom and performing a unitary transformation on this Hilbert space.Comment: 4 pages,3 figures, Two columns, LaTex2

Robustness of multiparty nonlocality to local decoherence

We investigate the robustness of multiparty nonlocality under local decoherence, acting independently and equally on each subsystems. To be specific, we consider an N-qubit GHZ state under depolarization, dephasing, or dissipation channel, and tested the nonlocality by violation of Mermin-Klyshko inequality, which is one of Bell's inequalities for multi-qubit systems. The results show that the robustness of nonlocality increases with the number of qubits, and that the nonlocality of an N-qubit GHZ state with even N is extremely persistent against dephasing.Comment: 5 pages, 4 figure

A generalized structure of Bell inequalities for bipartite arbitrary dimensional systems

We propose a generalized structure of Bell inequalities for arbitrary d-dimensional bipartite systems, which includes the existing two types of Bell inequalities introduced by Collins-Gisin-Linden-Massar-Popescu [Phys. Rev. Lett. 88, 040404 (2002)] and Son-Lee-Kim [Phys. Rev. Lett. 96, 060406 (2006)]. We analyze Bell inequalities in terms of correlation functions and joint probabilities, and show that the coefficients of correlation functions and those of joint probabilities are in Fourier transform relations. We finally show that the coefficients in the generalized structure determine the characteristics of quantum violation and tightness.Comment: 6 pages, 1 figur

Transport of Phosphate by Renal Brush Border Membrane Vesicle (BBMV) during Development - Role of the Growth Hormone-

It is well documented that plasma concentrations of Pi (inorganic phosphorus) are higher in developing subjects than in adults. In a previous study, we demonstrated that the Vmax (capacity) of the Na-Pi cotransport mechanism of the renal brush border membrane vesicles was higher in immature than mature rats. In this study, we evaluated the role of a growth hormone in the maintenance of a higher Vmax observed in immature rats. In mature rats, serum Pi, and the tubular reabsorption of Pi (TRPi) increased in the growth hormone treated animals. On the other hand, those values were not changed by growth hormone treatment in immature rats. In kinetic analysis, the Km (affinity) values were not different between the control (growth hormone-untreated) and growth hormone-treated renal brush border membrane vesicles in both immature and mature rats. The Vmax of the immature rats also was not changed by growth hormone treatment. On the contrary, Vmax increased significantly in the growth-hormone treated than the control mature rats. With the above findings, it seems that immature rats reabsorb Pi maximally even in the control state, and it is likely that a growth hormone is responsible for the phenomenon