509 research outputs found
Anisotropic quantum emitter interactions in two-dimensional photonic-crystal baths
Quantum emitters interacting with two-dimensional photonic-crystal baths
experience strong and anisotropic collective dissipation when they are
spectrally tuned to 2D Van-Hove singularities. In this work, we show how to
turn this dissipation into coherent dipole-dipole interactions with tuneable
range by breaking the lattice degeneracy at the Van-Hove point with a
superlattice geometry. Using a coupled-mode description, we show that the
origin of these interactions stems from the emergence of a qubit-photon bound
state which inherits the anisotropic properties of the original dissipation,
and whose spatial decay can be tuned via the superlattice parameters or the
detuning of the optical transition respect to the band-edges. Within that
picture, we also calculate the emitter induced dynamics in an exact manner,
bounding the parameter regimes where the dynamics lies within a Markovian
description. As an application, we develop a four-qubit entanglement protocol
exploiting the shape of the interactions. Finally, we provide a
proof-of-principle example of a photonic crystal where such interactions can be
obtained.Comment: 12 pages, 8 figure
Purely Long-Range Coherent Interactions in Two-Dimensional Structured Baths
In this work we study the quantum dynamics emerging when quantum emitters
exchange excitations with a two-dimensional bosonic bath with hexagonal
symmetry. We show that a single quantum emitter spectrally tuned to the middle
of the band relaxes following a logarithmic law in time due to the existence of
a singular point with vanishing density of states, i.e., the Dirac point.
Moreover, when several emitters are coupled to the bath at that frequency,
long-range coherent interactions between them appear which decay inversely
proportional to their distance without exponential attenuation. We analyze both
the finite and infinite system situation using both perturbative and
non-perturbative methods.Comment: 18 pages, 7 figures. Text restructured. Extended discussion on
experimental consideration
Mesoscopic entanglement induced by spontaneous emission in solid-state quantum optics
Implementations of solid-state quantum optics provide us with devices where qubits are placed at fixed positions in photonic or plasmonic one-dimensional waveguides. We show that solely by controlling the position ofthe qubits and withthe help of a coherent driving, collective spontaneous decay may be engineered to yield an entangled mesoscopic steady state. Our scheme relies on the realization of pure superradiant Dicke models by a destructive interference that cancels dipole-dipole interactions in one dimension
Tunable and robust long-range coherent interactions between quantum emitters mediated by Weyl bound states
Long-range coherent interactions between quantum emitters are instrumental
for quantum information and simulation technologies, but they are generally
difficult to isolate from dissipation. Here, we show how such interactions can
be obtained in photonic Weyl environments due to the emergence of an exotic
bound state whose wavefunction displays power-law spatial confinement. Using an
exact formalism, we show how this bound state can mediate coherent transfer of
excitations between emitters, with virtually no dissipation and with a transfer
rate that follows the same scaling with distance as the bound state
wavefunction. In addition, we show that the topological nature of Weyl points
translates into two important features of the Weyl bound state, and
consequently of the interactions it mediates: first, its range can be tuned
without losing the power-law confinement, and, second, they are robust under
energy disorder of the bath. To our knowledge, this is the first proposal of a
photonic setup that combines simultaneously coherence, tunability, long-range,
and robustness to disorder. These findings could ultimately pave the way for
the design of more robust long-distance entanglement protocols or quantum
simulation implementations for studying long-range interacting systems
Unconventional quantum optics in topological waveguide QED
The discovery of topological materials has challenged our understanding of
condensed matter physics and led to novel and unusual phenomena. This has
motivated recent developments to export topological concepts into photonics to
make light behave in exotic ways. Here, we predict several unconventional
quantum optical phenomena that occur when quantum emitters interact with a
topological waveguide QED bath, namely, the photonic analogue of the
Su-Schrieffer-Hegger model. When the emitters frequency lies within the
topological band-gap, a chiral bound state emerges, which is located at just
one side (right or left) of the emitter. In the presence of several emitters,
it mediates topological, long-range tunable interactions between them, that can
give rise to exotic phases such as double N\'eel ordered states. On the
contrary, when the emitters' optical transition is resonant with the bands, we
find unconventional scattering properties and different super/subradiant states
depending on the band topology. We also investigate the case of a bath with
open boundary conditions to understand the role of topological edge states.
Finally, we propose several implementations where these phenomena can be
observed with state-of-the-art technology.Comment: 17 pages, 10 figure
Heralded multiphoton states with coherent spin interactions in waveguide QED
WaveguideQEDoffers the possibility of generating strong coherent atomic
interactions either through appropriate atomic configurations in the
dissipative regime or in the bandgap regime. In this work, we show how to
harness these interactions in order to herald the generation of highly
entangled atomic states, which afterwards can be mapped to generate single mode
multi-photonic states with high fidelities.Weintroduce two protocols for the
preparation of the atomic states, we discuss their performance and compare them
to previous proposals. In particular, we show that one of them reaches high
probability of success for systems with many atoms but low Purcell factors
Quantum Spin Dynamics with Pairwise-Tunable, Long-Range Interactions
We present a platform for the simulation of quantum magnetism with full
control of interactions between pairs of spins at arbitrary distances in one-
and two-dimensional lattices. In our scheme, two internal atomic states
represent a pseudo-spin for atoms trapped within a photonic crystal waveguide
(PCW). With the atomic transition frequency aligned inside a band gap of the
PCW, virtual photons mediate coherent spin-spin interactions between lattice
sites. To obtain full control of interaction coefficients at arbitrary
atom-atom separations, ground-state energy shifts are introduced as a function
of distance across the PCW. In conjunction with auxiliary pump fields,
spin-exchange versus atom-atom separation can be engineered with arbitrary
magnitude and phase, and arranged to introduce non-trivial Berry phases in the
spin lattice, thus opening new avenues for realizing novel topological spin
models. We illustrate the broad applicability of our scheme by explicit
construction for several well known spin models.Comment: 18 pages, 10 figure
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