Quantum Probe Field Research Articles

Open quantum dynamics induced by light scalar fields

We consider the impact of a weakly coupled environment comprising a light scalar field on the open dynamics of a quantum probe field, resulting in a master equation for the probe field that features corrections to the coherent dynamics, as well as decoherence and momentum diffusion. The light scalar is assumed to couple to matter either through a nonminimal coupling to gravity or, equivalently, through a Higgs portal. Motivated by applications to experiments such as atom interferometry, we assume that the probe field can be initialized, by means of external driving, in a state that is not an eigenstate of the light scalar-field--probe system, and we derive the master equation for single-particle matrix elements of the reduced density operator of a toy model. We comment on the possibilities for experimental detection and the related challenges, and highlight possible pathways for further improvements. This derivation of the master equation requires techniques of non-equilibrium quantum field theory, including the Feynman-Vernon influence functional and thermo field dynamics, used to motivate a method of Lehmann-Symanzik-Zimmermann-like reduction. In order to obtain cutoff-independent results for the probe-field dynamics, we find that it is necessary to use a time-dependent renormalization procedure. Specifically, we show that non-Markovian effects following a quench, namely the violation of time-translational invariance due to finite-time effects, lead to a time-dependent modulation of the usual vacuum counterterms.

Dynamic generation and coherent control of beating stationary light pulses by a microwave coupling field in five-level cold atoms

We propose an efficient scheme for generating and controlling beating stationary light pulses in a five-level atomic sample driven into electromagnetically induced transparency condition. This scheme relies on an asymmetrical procedure of light storage and retrieval tuned by two counter-propagating control fields where an additional coupling field, such as the microwave field, is introduced in the retrieval stage. A quantum probe field, incident upon such an atomic sample, is first transformed into spin coherence excitation of the atoms and then retrieved as beating stationary light pulses exhibiting a series of maxima and minima in intensity due to the alternative constructive and destructive interference. It is convenient to control the beating stationary light pulses just by manipulating the intensity and detuning of the additional microwave field. This interesting phenomenon involves in fact the coherent manipulation of dark-state polaritons and could be explored to achieve the efficient temporal splitting of stationary light pulses and accurate measurement of the microwave intensity.

Cooperative nonlinear grating sensitive to light intensity and photon correlation.

Utilizing dipole blockade of Rydberg excitations, we study an ensemble of stationary atoms driven into the four-level N configuration for achieving a new kind of electromagnetically induced grating in the presence of a traveling-wave and a standing-wave classical control fields. This grating shows cooperative optical nonlinearities as manifested by the sensitivity of output diffraction patterns to input light intensities (photon correlations) of a quantum probe field, promising then an essential opportunity for distinguishing weaker and stronger (bunched and anti-bunched) light fields.

Generating and manipulating beating signals by a microwave field in four-level cold atoms

We propose an efficient scheme for the dynamic generation and manipulation of beating signals in a sample of cold atoms driven into the four-level quasi-Λ configuration. This scheme relies on a procedure of light storage and retrieval controlled by a classical coupling field with a microwave field introduced only in the retrieval stage. One quantum probe field, incident upon this atomic sample, is transformed into a collective excitation of atomic spin coherence and then into two optical components characterized by different time-dependent phases. Consequently the retrieved quantum probe field exhibits a series of maxima and minima (beating signals) in intensity due to the alternative constructive and destructive interference. This interesting phenomenon, in fact, involves the coherent conversion between single-mode and two-mode dark-state polaritons and could be explored to measure the microwave intensity with high-precision beating signals.

Coherent generation and dynamic manipulation of double stationary light pulses in a five-level double-tripod system of cold atoms

We study a five-level double-tripod system of cold atoms for efficiently manipulating the dynamic propagation and evolution of a quantum probe field by modulating four classical control fields. Our numerical results show that it is viable to transform the quantum probe field into a pair of two-color stationary light pulses mutually coupled through two wave packets of atomic spin coherence. The pair of stationary light pulses can be released either from the sample entrance and exit synchronously or just from the sample exit with a controlled time delay. In addition, the two-color stationary light pulses are immune to the fast decay originating from the higher-order Fourier components of atomic spin and optical coherence, and may exhibit the quantum limited beating signals with their characteristic frequency determined by detunings of the four classical control fields. These results could be explored to design novel photonic devices, such as optical routing, beam splitter, and beat generator, for manipulating a quantum light field.

Dynamic generation of robust and controlled beating signals in an asymmetric procedure of light storage and retrieval

We propose an efficient scheme for the robust and controlled generation of beating signals in a sample of stationary atoms driven into the tripod configuration. This scheme relies on an asymmetric procedure of light storage and retrieval where the two classical coupling fields have equal detunings in the storage stage but opposite detunings in the retrieval stage. A quantum probe field, incident upon such an atomic sample, is first transformed into two spin coherence wave-packets and then retrieved with two optical components characterized by different time-dependent phases. Therefore the retrieved quantum probe field exhibits a series of maxima and minima (beating signals) in intensity due to the alternative constructive and destructive interference. This interesting phenomenon involves in fact the coherent manipulation of two dark-state polaritons and may be explored to achieve the fast quantum limited measurement.

The property of quantum noise in active Raman gain medium

We study a three-level atom assemble interacting with a pump field and a quantum probe field, and derive the Langevin quantum noise operators and quantum noise spectrum due to vacuum fluctuations via quantum theory. We calculate the output noise spectrum of active Raman scattering field through the medium when introducing one nonclassical squeezing field.

Non-Abelian geometric quantum memory with an atomic ensemble

We study a quantum information storage scheme based on an atomic ensemble with near (also exact) three-photon resonance electromagnetically induced transparency (EIT). Each 4-level-atom is coupled to two classical control fields and a quantum probe field. Quantum information is adiabatically stored in the associated dark polariton manifold. An intrinsic nontrivial topological structure is discovered in our quantum memory implemented through the symmetric collective atomic excitations with a hidden $\mathrm{SU}(3)$ dynamical symmetry. By adiabatically changing the Rabi frequencies of two classical control fields, the quantum state can be retrieved up to a non-Abelian holonomy and thus decoded from the final state in a purely geometric way.

Quantum memory based on $\mathsf{\Lambda}$-atoms ensemble with two-photon resonance EIT

We study the $\Lambda$-atoms ensemble based quantum memory for the storage of the quantum information carried by a probe light field. Two atomic Rabi transitions of the ensemble are coupled to the quantum probe field and classical control field respectively with a same detuning. Making use of the hidden symmetry analysis developed recently for the on-resonance EIT case (Sun, Li, and Liu, Phys. Rev. Lett. 91, 147903 (2003)), we show that the dark states and dark-state polaritons can still exist for the case of two-photon resonance EIT. Starting from these dark states we construct a complete class of eigen-states of the total system. A explicit form of the adiabatic condition is also given in order to achieve the memory and retrieve of quantum information.

Preparation of multiparty entangled states using pairwise perfectly efficient single-probe photon four-wave mixing

We propose a scheme to achieve multiparty entanglement with perfectly efficient, ultraslow, multichannel pairwise four-wave mixing (FWM). A cold atomic medium is illuminated with an $N$-mode continuous-wave (cw) control laser to produce coherent mixtures of excited states. An ultraslowly propagating, single-photon quantum probe field completes multichannel, pairwise FWM, creating a depth dependent entanglement of $N$ Fock states. We show explicitly that this scheme can be utilized to realize an $N$-party entangled state of ultraslowly propagating quantized fields. In particular, we give the explicit analytical expression of a three-party W-state propagating at an ultraslow group velocity, and the numerical results of a multiparty W state of $2M+1$ Fock states.

Group velocity of a probe light in an ensemble ofΛatoms under two-photon resonance

We study the propagation of a probe light in an ensemble of $\Lambda$-type atoms, utilizing the dynamic symmetry as recently discovered when the atoms are coupled to a classical control field and a quantum probe field {[Sun {\it et al.,} Phys. Rev. Lett. {\bf 91}, 147903 (2003)]}. Under two-photon resonance, we calculate the group velocity of the probe light with collective atomic excitations. Our result gives the dependence of the group velocity on the common one-photon detuning, and can be compared with the recent experiment (E. E. Mikhailov, Y. V. Rostovtsev, and G. R. Welch, quant-ph/0309173).

Multiorder coherent Raman scattering of a quantum probe field

We study the multiorder coherent Raman scattering of a quantum probe field in a far-off-resonance medium with a prepared coherence. Under the conditions of negligible dispersion and limited bandwidth, we derive a Bessel-function solution for the sideband field operators. We analytically and numerically calculate various quantum statistical characteristics of the sideband fields. We show that the multiorder coherent Raman process can replicate the statistical properties of a single-mode quantum probe field into a broad comb of generated Raman sidebands. We also study the mixing and modulation of photon statistical properties in the case of two-mode input. We show that the prepared Raman coherence and the medium length can be used as control parameters to switch a sideband field from one type of photon statistics to another type, or from a non-squeezed state to a squeezed state and vice versa.

Quantum entanglement of Fock states with perfectly efficient ultraslow single-probe photon four-wave mixing.

We propose a method to achieve quantum entanglement of two Fock states with perfectly efficient, ultraslow propagation enhanced four-wave mixing. A cold atomic medium is illuminated with a two-mode cw control laser to produce coherent mixtures of excited states. An ultraslowly propagating, single-photon quantum probe field completes the four-wave mixing with 100% photon flux conversion efficiency, creating a depth dependent entanglement of two Fock states. We show that at a suitable propagation distance, a maximum entangled state is created with a single-photon wave-packet state that has 50% probability of being in each of two product-type Fock states.

Parametric beating of a quantum probe field with a prepared Raman coherence in a far-off-resonance medium

We investigate the parametric beating of a quantum probe field with a prepared Raman coherence in a far-off-resonance medium, and describe the resulting multiplexing processes. We show that the normalized autocorrelation functions of the probe field are exactly reproduced in the Stokes and anti-Stokes sideband fields. We find that an initial coherent state of the probe field can be replicated to the Raman sidebands, and an initial squeezing of the probe field can be partially transferred to the sidebands. We show that a necessary condition for the output fields to be in an entangled state or, more generally, in a nonclassical state is that the input field state is a nonclassical state.