Single-photon Packet Research Articles

Decoherence of a One-Photon Packet in an Imperfect Optical Fiber

The Liouville equation describing the time development of the density matrix of a single-photon packet propagating in an optical fiber is investigated. The Hamiltonian of the dynamic system and the relaxation operator depend on the phenomenological parameters: chromatic dispersion, polarization mode dispersion, polarization mode loss, and differential group delay. The patterns of distortion of a quantum packet are compared to the laws known from classical representations.

Work on a quantum dipole by a single-photon pulse.

Energy transfer from a quantized field to a quantized dipole is investigated. We find that a single photon can transfer energy to a two-level dipole by inducing a dynamic Stark shift, going beyond the well-known absorption and emission processes. A quantum thermodynamical perspective allows us to unravel these two energy transfer mechanisms and to identify the former as a generalized work and the latter as a generalized heat. We show two necessary conditions for the generalized work transfer by a single photon to occur, namely, off-resonance and finite linewidth of the pulse. We also show that the generalized work performed by a single-photon pulse equals the reactive (dispersive) contribution of the work performed by a semiclassical pulse in the low-excitation regime.

Quantum Filtering for Tavis-Cummings System

In this work, Interaction of a Tavis-Cummings system with single photon packet is studied by quantum master and filter equations with considering homodyne detector. We present result of simulation for two two-level atoms and analyze effects of adding an external single-photon magnetic field.

Bayesian modelling of uncertainties of Monte Carlo radiative-transfer simulations

One of the big challenges in astrophysics is the comparison of complex simulations to observations. As many codes do not directly generate observables (e.g. hydrodynamic simulations), the last step in the modelling process is often a radiative-transfer treatment. For this step, the community relies increasingly on Monte Carlo radiative transfer due to the ease of implementation and scalability with computing power. We consider simulations in which the number of photon packets is Poisson distributed, while the weight assigned to a single photon packet follows any distribution of choice. We show how to estimate the statistical uncertainty of the sum of weights in each bin from the output of a single radiative-transfer simulation. Our Bayesian approach produces a posterior distribution that is valid for any number of packets in a bin, even zero packets, and is easy to implement in practice. Our analytic results for large number of packets show that we generalise existing methods that are valid only in limiting cases. The statistical problem considered here appears in identical form in a wide range of Monte Carlo simulations including particle physics and importance sampling. It is particularly powerful in extracting information when the available data are sparse or quantities are small.

Quantum filtering equations for atom-single photon interaction by homodyne detection: Considering full interaction Rabi model

Interaction of a two level atom with a single photon packet is investigated by considering full interaction model of Rabi model. A homodyne measurement providence information about the photon-atom system. Quantum filtering equations for this system are found and the results are discussed. Effects of adding an external magnetic field that is explained.

Dynamic Stark shift induced by a single photon packet.

The dynamic Stark shift results from the interaction of an atom with the electromagnetic field. We show how a propagating single-photon wave packet can induce a time-dependent dynamical Stark shift on a two-level system (TLS). A non-perturbative fully quantum treatment is employed, where the quantum dynamics of both the field and the TLS are analyzed. We also provide the means to experimentally access such time-dependent frequency by measuring the interference pattern in the electromagnetic field inside a 1D waveguide. The effect we evidence here may find applications in the autonomous quantum control of quantum systems without classical external fields, which can be useful for quantum information processing as well as for quantum thermodynamical tasks.

Non-Markovianity induced by a single-photon wave packet in a one-dimensional waveguide.

The concept of non-Markovianity (NM) in quantum dynamics is still an open debate. Understanding how to generate and measure NM in specific models may aid in this quest. In quantum optics, an engineered electromagnetic environment coupled to a single atom can induce NM. The most common scenario of structured electromagnetic environment is an optical cavity, composed by a pair of mirrors. Here, we show how to generate and measure NM on a two-level system coupled to a one-dimensional waveguide with no mirrors required. The origin of the non-Markovian behavior lies in the initial state of the field, prepared as a single-photon packet. NM is shown to depend on two experimentally controllable parameters, namely, the linewidth of the packet and its central frequency. We relate the presence of NM to quantum interference. We also show how the two output channels of the waveguide provide distinct signatures of NM, both experimentally accessible.

On the simultaneous measurement of the energy and arrival time of a photon

The simultaneous measurement of the energy and arrival time of a single-photon packet, as well as the experimental implementation of such a measurement with the use of a parametric transformation upward in the energy (up conversion), is proposed.

Single-photon scattering and quantum-state transformations in cavityQED

We investigate quantum scattering of a single photon packet from a $\ensuremath{\Lambda}$-type three-level atom confined in an optical cavity. The evolution of the coupled system is analyzed by projecting the quantum state onto ``dark'' and ``bright'' states. In the asymptotic long time limit, quantum interference between these states is determined by a frequency-dependent phase angle. We present an analytic expression of such a scattering phase factor, and indicate how it leads to a family of transformations between polarization states of the photon and atom. Specific examples include quantum state swapping and the generation of maximally entangled states.