Imran M. Mirza

Multiqubit entanglement in bidirectional-chiral-waveguide QED

We study the generation of entanglement induced by a single-photon Gaussian wavepacket in multi-atom bi-directional waveguide QED. In particular, we investigate the effect of increasing the number of atoms on the average pairwise entanglement. We demonstrate by selecting smaller decay rates and in chiral waveguide settings, that both entanglement survival times and maximum generated entanglement can be increased by at least a factor of 3/2, independent of the number of atoms. In addition, we analyze the influence of detuning and delays on the robustness of the generated entanglement. There are potential applications of our results in entanglement based multi-qubit quantum networks

Two-photon entanglement in multiqubit bidirectional-waveguide QED

We study entanglement generation and control in bi-directional waveguide QED driven by a two photon Gaussian wavepacket. In particular, we focus on how increasing the number of qubits affects the overall average pairwise entanglement in the system. We also investigate how the presence of a second photon can introduce non-linearities, thereby manipulating the generated entanglement. In addition, we show that through the introduction of chirality and small decay rates, entanglement can be stored and enhanced up to factors of 2 and 3, respectively. Finally, we analyze the influence of finite detunnings and time-delays on the generated entanglement.

Single-photon time-dependent spectra in quantum optomechanics

We consider how a single photon can probe the quantum nature of a moving mirror in the context of quantum optomechanics. In particular, we demonstrate how the single-photon spectrum reveals resonances that depend on how many phonons are created as well as on the strength of the mirror-photon interaction. A dressed-state picture is used to explain positions and relative strengths of those resonances. The time-dependent spectrum shows how the resonances are built up over time by the photon interacting with the moving mirror.

Influence of disorder on electromagnetically induced transparency in chiral waveguide quantum electrodynamics

We study single-photon transport in a one-dimensional disordered lattice of three-level atoms coupled to an optical waveguide. In particular, we study atoms of Λ-type that are capable of exhibiting electromagnetically induced transparency and separately consider disorder in the atomic positions and transition frequencies. We mainly address the question of how preferential emission into waveguide modes (chirality) can influence the formation of spatially localized states. Our work has relevance to experimental studies of cold atoms coupled to nanoscale waveguides and has possible applications to quantum communications.

Chirality, band structure, and localization in waveguide quantum electrodynamics

Architectures based on waveguide quantum electrodynamics have emerged as promising candidates for quantum networks. In this paper, we analyze the propagation of single photons in disordered many-atom waveguides. We pay special attention to the influence of chirality (directionality of photon transport) on the formation of localized photonic states, considering separately the cases of disorder in the atomic positions and in the atomic transition frequencies.