Quantum Data Hiding

We expand on our work on Quantum Data Hiding -- hiding classical data among parties who are restricted to performing only local quantum operations and classical communication (LOCC). We review our scheme that hides one bit between two parties using Bell states, and we derive upper and lower bounds on the secrecy of the hiding scheme. We provide an explicit bound showing that multiple bits can be hidden bitwise with our scheme. We give a preparation of the hiding states as an efficient quantum computation that uses at most one ebit of entanglement. A candidate data hiding scheme that does not use entanglement is presented. We show how our scheme for quantum data hiding can be used in a conditionally secure quantum bit commitment scheme.Comment: 19 pages, IEEE style, 8 figures, submitted to IEEE Transactions on Information Theor

Root induction in radiata pine using Agrobacterium rhizogenes

Root induction using Agrobacterium rhizogenes was conducted in hypocotyl explants, intact seedlings, de-rooted seedling cuttings and adventitious shoots of radiata pine ( Pinus radiata D. Don). Use of two A. rhizogenes strains (A4T and LB9402), with or without application of IBA, can trigger root formation in different explants. Strain LBA9402 was more effective than A4T in increasing rooting percentage and root number. Addition of 4.4 uMIBA to the medium further enhanced rooting from the cultured hypocotyl segments inoculated with the two A. rhizogenes strains. Strain LBA9402+IBA induced in about 75% of the cultured hypocotyl segments to form roots. In contrast the controls failed to initiate roots on intact seedlings or cultured segments in presence or absence of IBA. Rooting of adventitious shoots from 3 year-old radiata pine was improved following inoculation with LBA9402, suggesting that this rooting treatment has potential to aid clonal propagation of radiata pine

Locking classical correlation in quantum states

We show that there exist bipartite quantum states which contain large hidden classical correlation that can be unlocked by a disproportionately small amount of classical communication. In particular, there are $(2n+1)$-qubit states for which a one bit message doubles the optimal classical mutual information between measurement results on the subsystems, from $n/2$ bits to $n$ bits. States exhibiting this behavior need not be entangled. We study the range of states exhibiting this phenomenon and bound its magnitude.Comment: 7 pages, revtex

The entanglement of purification

We introduce a measure of both quantum as well as classical correlations in a quantum state, the entanglement of purification. We show that the (regularized) entanglement of purification is equal to the entanglement cost of creating a state $\rho$ asymptotically from maximally entangled states, with negligible communication. We prove that the classical mutual information and the quantum mutual information divided by two are lower bounds for the regularized entanglement of purification. We present numerical results of the entanglement of purification for Werner states in ${\cal H}_2 \otimes {\cal H}_2$.Comment: 12 pages RevTex, 1 figure, to appear in JMP special issue on quantum information. v3 contains additional references, motivation, and a small change in the figur

Hiding bits in Bell states

We present a scheme for hiding bits in Bell states that is secure even when the sharers Alice and Bob are allowed to carry out local quantum operations and classical communication. We prove that the information that Alice and Bob can gain about a hidden bit is exponentially small in $n$, the number of qubits in each share, and can be made arbitrarily small for hiding multiple bits. We indicate an alternative efficient low-entanglement method for preparing the shared quantum states. We discuss how our scheme can be implemented using present-day quantum optics.Comment: 4 pages RevTex, 1 figure, various small changes and additional paragraph on optics implementatio

Response of Arabidopsis thaliana seedlings to lead exposure: effect of pre-treatment with sodium nitroprusside

Plants are regularly exposed to unfavorable conditions that impose stress. Lead (Pb), is one of the major pollutants in the environment that causes serious public health and environmental concerns. Increasing levels of lead could also have severe consequences for plants. Plants exposed to lead stress initiate signaling pathways, and make specific changes in their cell physiology and metabolism to avoid or tolerate the stress. However, mechanisms to reduce the effects of lead may vary from plant to plant, developmental stage, and culture medium. Nitric oxide is an important signaling molecule in plant development and defense responses. It has been shown to play a major role in plant responses to several abiotic stresses, such as heat, chilling, drought, salt, UV irradiation and ozone exposure. The objective of this study is to examine the physiological responses to Pb exposure of Arabidopsis thaliana seeds pre-treated with sodium nitroprusside (SNP), a nitric oxide donor. All experiments were carried out using 7-day-old seedlings in a laboratory environment. Pb contents were determined using a graphite furnace spectrometer. Antioxidant assays and reactive oxygen species were carried out using a microplate reader. A major finding is that Pb treatment resulted in increased oxidative stress, which was counteracted by SNP pre-treatment. This and other results obtained are discussed in relation to a strategy to tolerate Pb accumulation in plant cells

Quantum Channel Capacity of Very Noisy Channels

We present a family of additive quantum error-correcting codes whose capacities exceeds that of quantum random coding (hashing) for very noisy channels. These codes provide non-zero capacity in a depolarizing channel for fidelity parameters $f$ when $f> .80944$. Random coding has non-zero capacity only for $f>.81071$; by analogy to the classical Shannon coding limit, this value had previously been conjectured to be a lower bound. We use the method introduced by Shor and Smolin of concatenating a non-random (cat) code within a random code to obtain good codes. The cat code with block size five is shown to be optimal for single concatenation. The best known multiple-concatenated code we found has a block size of 25. We derive a general relation between the capacity attainable by these concatenation schemes and the coherent information of the inner code states.Comment: 31 pages including epsf postscript figures. Replaced to correct important typographical errors in equations 36, 37 and in tex