Coherent information

About: Coherent information is a research topic. Over the lifetime, 1225 publications have been published within this topic receiving 46672 citations.

The phase operator in quantum information processing

Abstract: It is shown that unitary depolarizers, which play an important role in quantum information processing, can be constructed in terms of the Pegg-Barnett phase operator. By using the result, the classical information capacity of quantum dense coding with unitary encoding in a finite-dimensional Hilbert space is derived. Furthermore, the relation between the capacity of quantum dense coding and the coherent information of a noisy quantum channel is obtained.

Impossibility of perfect quantum sealing of classical information

Abstract: Sealing information means making it publicly available, but with the possibility of knowing if it has been read. Commenting on Ref. 1, we will show that perfect quantum sealing is not possible for perfectly retrievable information, due to the possibility of performing a perfect measurement without disturbance, even on unknown states. The measurement is a collective one, and this makes the protocol of quantum sealing very interesting as the only example of the power of collective measurements in breaking security.

Quantum-optical nature of the recollision process in high-order-harmonic generation

Abstract: Coherent processing of quantum information and attosecond science have had so far little in common. We here show that recent data in high harmonic emission reveal a realization of a qubit and its coherent manipulation at the attosecond time scale. By observing the interference pattern created by the spatiotemporal overlap of photons emitted by two interfering electron paths we generate a photon Hadamard gate and thus erase the electron-trajectory information. This allows the measurement of the relative phase in electron-trajectory quantum superpositions which realize the qubit, opening the possibility for more elaborate schemes of coherent information processing within high-field physics.

Conditional Information and Hidden Correlations in Single-qudit States

Abstract: We discuss the notions of mutual information and conditional information for noncomposite systems, classical and quantum; both the mutual information and the conditional information are associated with the presence of hidden correlations in the state of a single qudit. We consider analogs of the entanglement phenomena in the systems without subsystems related to strong hidden quantum correlations.

Nonclassical statistical properties of finite-coherent states in the framework of the Jaynes–Cummings model

Abstract: Adopting the framework of the nonresonant Jaynes–Cummings model, we investigate the nonclassical statistical properties of coherent states defined in a finite-dimensional Hilbert space, considering the single-mode cavity field prepared in a finite and discrete harmonic oscillator-like coherent state with a small average number of photons. Explicit expressions for the time evolution of various functions characterizing the quantum state, such as the Mandel's Q parameter, the photon-number distribution and its respective entropy, the discrete Wigner function, and the number-phase uncertainty relation, are investigated in detail. We also show that the atomic inversion possesses regular structures with collapses and revivals in the Rabi oscillations since the detuning between atom and field is large as compared to the coupling constant, i.e., ( κ /2 g ) 2 ⪢1. The numerical and analytical results obtained in this work turn evident the quantum interference effects between the components of the finite-coherent states. Furthermore, we present a discussion about unitary depolarizers in finite-dimensional Hilbert space and their connection to quantum information theory.