Quantum cryptography by modulating spontaneous photon emissions

Alicia Sit, Felix Hufnagel, Ebrahim Karimi

Hideaki Matsueda, Fumiaki Shibata, Chikako Uchiyama

A novel method of quantuIn cryptography is proposed, together with a mathemat- ical theory on the basis of nonequilibrium statistical mechanics.The proposed method involves the controlled randomness in the spontaneous emission of photons.Uncertainties in spontaneous photon emission, beam-splitting, and superposition improve the crypto- graphic security.A quantum communication channel is mathematically equivalent to a model of spin relax- ation when the Schwinger bosons are introduced.Effects of quantum mechanical devices on the propagating signals are expressed as rotation operators in the spin coherent state representation.Effect of an eavesdropper is represented by a phase shifter.The concept of"controlled randomness" is introduced to construct quantum cryptographic systems.This could be implemented by using microcavities with which the rate of spontaneous emission is controlled.In theory, this controlled randomness is analyzed with the use of the Kubo-Anderson model of spin relaxation.

Kwiat, White, Peterson +2 more

Bin Zhang, Reuven Ianconescu, A. Friedman +4 more

It has been shown that the spontaneous emission rate of photons by free electrons, unlike stimulated emission, is independent of the shape or modulation of the quantum electron wavefunction (QEW). Nevertheless, here we show that the quantum state of the emitted photons is non-classical and does depend on the QEW shape. This non-classicality originates from the shape dependent off-diagonal terms of the photon density matrix. This is manifested in the Wigner distribution function and would be observable experimentally through homodyne detection techniques as a squeezing effect. Considering a scheme of electrons interaction with a single microcavity mode, we present a QED formulation of spontaneous emission by multiple modulated QEWs through a build-up process. Our findings indicate that in the case of a density modulated QEWs beam, the phase of the off-diagonal terms of the photon state emitted by the modulated QEWs is the harbinger of bunched beam superradiance, where the spontaneous emission is proportional toNe2. This observation offers a potential for enhancement of other quantum electron interactions with quantum systems by a modulated QEWs beam carrying coherence and quantum properties of the modulation.

Bin Zhang, Reuven Ianconescu, A. Friedman +4 more

It has been shown that the spontaneous emission rate of photons by free electrons, unlike stimulated emission, is independent of the shape or modulation of the quantum electron wavefunction (QEW). Nevertheless, here we show that the quantum state of the emitted photons is non-classical and does depend on the QEW shape. This non-classicality originates from the shape dependent off-diagonal terms of the photon density matrix. This is manifested in the Wigner distribution function and would be observable experimentally through Homodyne detection techniques as a squeezing effect. Considering a scheme of electrons interaction with a single microcavity mode, we present a QED formulation of spontaneous emission by multiple modulated QEWs through a build-up process. Our findings indicate that in the case of a density modulated QEWs beam, the phase of the off-diagonal terms of the photon state emitted by the modulated QEWs is the harbinger of bunched beam superradiance, where the spontaneous emission is proportional to N_e^2. This observation offers a potential for enhancement of other quantum electron interactions with quantum systems by a modulated QEWs beam carrying coherence and quantum properties of the modulation.

Alexander V. Sergienko, Alan L. Migdall, Raju V. Datla