We present an exact dissipation model for correlated photon transport in waveguide QED systems. This rigorously incorporates the infinitely many degrees of freedom full three-dimensional photonic scattering channels non-excitable ambient environment. show that leakages to can be accounted by a reduced Hamiltonian and restricted eigen-state, with resultant atomic dissipation. is valid arbitrary Fock coherent states.

Quantum Key Distribution (QKD) theoretically provides information-theoretic security based on physical laws. However, imperfections in practice lead to the possibility of quantum hacking QKD implementation, especially passive attacks that are difficult be detected. In this paper, we study experimentally and upper limit a backflash attack, as one vital attacks, fiber-based system. We demonstrate attack full equipped receiver show its feasibility limited distinguish ratio decoding. More...

Using an entanglement-preserving approach, we theoretically study the reservoir-induced photonic dissipations in waveguide quantum electrodynamic (wQED) systems coupled to excitable reservoir consisting of oscillators. For single-photon case, show that effects dissipation can be described by a reduced Hamiltonian and restricted eigenstate. multiphoton approach is, general, not valid. Nonetheless, identify weak-reservoir condition for approximately valid, which applies majority current...

We study computationally the effects of dissipations on correlated two-photon transport in waveguide--quantum-electrodynamic systems. show that dissipative regime, correlation signatures remain prominent even when can be described by a single-photon picture. Moreover, varying dissipation, photonic have an induced transition from bunching to antibunching, and vice versa, depending input quantum state.

A recent experiment reveals the linear scaling property of superradiant emission rate for a trapped atom cloud that is excited by weak and short light pulses. We adopt real-space approach to numerically demonstrate such law can be interpreted as single-photon superradiance, in both time domain frequency domain. The dependence on distance between atoms investigated. further study superradiance artificial have deviations transition frequencies decay rates.

We study the correlation signatures of a coherent three-photon scattering process by computationally investigating photon wavefunctions, functions, and nonlinear conditional phases. It is shown that both bound states hybrid states, which consist two-photon one unbound photon, contribute to all signatures. All computational are in good agreement with recent experiment, wherein weak photonic state propagates through quantum Rydberg medium [Liang et al., Science359, 783...

As a manifestation of cooperative interactions between single photon and cluster atoms, single-photon superradiance has attracted considerable attention recently but been studied insofar as that only quantum emitters are involved in the process. Here we expand scope investigation to study waveguide-quantum-electrodynamical system containing whispering-gallery-mode (WGM) resonators which essential for many nanophotonic devices. It is shown analytically numerically can also occur when WGM...

Quantum key distribution (QKD), guaranteed by the principle of quantum physics, is a promising solution for future secure information and communication technology. However, device imperfections compromise security real-life QKD systems, restricting wide deployment QKD. This study reports decoy-state Bennett-Brassard 1984 (BB84) experiment that considers both source detection imperfections. In particular, we achieve rigorous finite-key bound over fiber links up to 75 km applying systematic...

Photons are appealing as flying quantum bits due to their low-noise, long coherence times, light-speed transmission, and ease of manipulation at the single-qubit level using standard optical components such beam splitters waveguides. The challenge in information processing has been realization two-qubit gates for photonic qubits lack highly efficient Kerr nonlinearities single-photon level. To date, only probabilistic controlled-phase based on linear optics projective measurement photon...

We propose an exact analytical approach to study the single-photon spontaneous emissions in waveguide quantum electrodynamic (QED) systems. Using ab initio evolution technique, our provides a universal framework investigate full spatiotemporal dynamics of atomic response, cavity and emitted photonic wave functions. The validity is numerically confirmed. Our rigorous can be extensively applied more complicated QED architectures. Moreover, such readily incorporate effects dissipations has...

In a waveguide-QED system, under certain condition, the spontaneous emission rate of an atom cloud with single excitation can be enhanced. Single-photon superradiance refers to case when enhancement attains its maximum. We show that exhibiting single-photon described by effective two-level system. also adopt real space numerical approach validate understanding using such mapping picture. further numerically investigate superradiant state and dark state.

Reference-frame-independent measurement-device-independent quantum key distribution is a promising candidate for building star-type secure networks because it does not require reference alignment and removes all detector-side-channel attacks. However, prior works considered only symmetric case in which the channels of both users have same loss. In realistic network, losses various are likely to be different owing their geographical locations. this study, we present an asymmetric protocol...

The intensity correlations due to imperfect modulation during the quantum-state preparation in a measurement-device-independent quantum key distribution (MDI QKD) system compromise its security performance. Therefore, it is crucial assess impact of on practical MDI QKD systems. In this work, we propose theoretical model that quantitatively analyzes secure rate systems under correlations. Furthermore, apply with measured correlations, which shows struggles generate keys efficiently model. We...

The intensity correlations due to imperfect modulation during the quantum-state preparation in a measurement-device-independent quantum key distribution (MDI QKD) system compromise its security performance. Therefore, it is crucial assess impact of on practical MDI QKD systems. In this work, we propose theoretical model that quantitatively analyzes secure rate systems under correlations. Furthermore, apply with measured correlations, which shows struggles generate keys efficiently model. We...

To resolve the intrinsic trade-off between deterministic nature and scalability of controlled phase gate implementation in linear optics regime, we propose a novel two-photon scheme chiral quantum nanophotonics. The essential ingredient here is that, non-linear π-phase shift imprinted during photonic molecule generations. On one hand, operates way without assistance probabilistic ancilla qubit measurement. other low complexity to be highly scalable. date, coupling readily underpinned by...

To enhance the spatial utility of typical two-port Hadamard gate, we propose a novel single-channel scheme through frequency conversion in Λ-atom-mediated single-photon Raman scattering process chiral quantum nanophotonics. We demonstrate faithful and efficient gate operations, quantitatively analyze performance. Moreover, by manipulating photon-emitter coupling detuning, it is confirmed that an arbitrary unitary single-qubit operations are achieved presented configuration, including most...

Atom coherence in the cooperative interaction between atoms and a single photon creates ultrafast spontaneous emission ultrastrong intensity peaks, namely single-photon superradiance, which has attracted considerable research interest recent years. As investigation for such superradiance usually involves only quantum emitters, this paper we present atom-photon system including whispering gallery mode resonators, are one of most essential components nanophotonic devices. Here both...

We present a theoretical analysis of multi-photon transport in the presence reservoir, and unearth breakdown widely adopted non-Hermitian Hamiltonian descriptions dissipative regime due to reservoir-induced changes correlations. © 2019 The Author(s)