188 research outputs found
Two-particle bosonic-fermionic quantum walk via 3D integrated photonics
Quantum walk represents one of the most promising resources for the
simulation of physical quantum systems, and has also emerged as an alternative
to the standard circuit model for quantum computing. Up to now the experimental
implementations have been restricted to single particle quantum walk, while
very recently the quantum walks of two identical photons have been reported.
Here, for the first time, we investigate how the particle statistics, either
bosonic or fermionic, influences a two-particle discrete quantum walk. Such
experiment has been realized by adopting two-photon entangled states and
integrated photonic circuits. The polarization entanglement was exploited to
simulate the bunching-antibunching feature of non interacting bosons and
fermions. To this scope a novel three-dimensional geometry for the waveguide
circuit is introduced, which allows accurate polarization independent
behaviour, maintaining a remarkable control on both phase and balancement.Comment: 4 pages, 5 figures + supplementary informatio
Integrated optical waveplates for arbitrary operations on polarization-encoded single-qubits
Integrated photonic technologies applied to quantum optics have recently
enabled a wealth of breakthrough experiments in several quantum information
areas. Path encoding was initially used to demonstrate operations on single or
multiple qubits. However, a polarization encoding approach is often simpler and
more effective. Two-qubits integrated logic gates as well as complex
interferometric structures have been successfully demonstrated exploiting
polarization encoding in femtosecond-laser-written photonic circuits. Still,
integrated devices performing single-qubit rotations are missing. Here we
demonstrate waveguide-based waveplates, fabricated by femtosecond laser pulses,
capable to effectively produce arbitrary single-qubit operations in the
polarization encoding. By exploiting these novel components we fabricate and
test a compact device for the quantum state tomography of two
polarization-entangled photons. The integrated optical waveplates complete the
toolbox required for a full manipulation of polarization-encoded qubits
on-chip, disclosing new scenarios for integrated quantum computation, sensing
and simulation, and possibly finding application also in standard photonic
devices
Anderson localization of entangled photons in an integrated quantum walk
Waves fail to propagate in random media. First predicted for quantum
particles in the presence of a disordered potential, Anderson localization has
been observed also in classical acoustics, electromagnetism and optics. Here,
for the first time, we report the observation of Anderson localization of pairs
of entangled photons in a two-particle discrete quantum walk affected by
position dependent disorder. A quantum walk on a disordered lattice is realized
by an integrated array of interferometers fabricated in glass by femtosecond
laser writing. A novel technique is used to introduce a controlled phase shift
into each unit mesh of the network. Polarization entanglement is exploited to
simulate the different symmetries of the two-walker system. We are thus able to
experimentally investigate the genuine effect of (bosonic and fermionic)
statistics in the absence of interaction between the particles. We will show
how different types of randomness and the symmetry of the wave-function affect
the localization of the entangled walkers.Comment: 7 pages, 5 figures, revised version published on Nature Photonics 7,
322-328 (2013
Path-polarization hyperentangled and cluster states of photons on a chip
Encoding many qubits in different degrees of freedom (DOFs) of single photons
is one of the routes towards enlarging the Hilbert space spanned by a photonic
quantum state. Hyperentangled photon states (i.e. states showing entanglement
in multiple DOFs) have demonstrated significant implications for both
fundamental physics tests and quantum communication and computation. Increasing
the number of qubits of photonic experiments requires miniaturization and
integration of the basic elements and functions to guarantee the set-up
stability. This motivates the development of technologies allowing the precise
control of different photonic DOFs on a chip. We demonstrate the contextual use
of path and polarization qubits propagating within an integrated quantum
circuit. We tested the properties of four-qubit linear cluster states built on
both DOFs. Our results pave the way towards the full integration on a chip of
hybrid multiqubit multiphoton states.Comment: 7 pages, 7 figures, RevTex4-1, Light: Science & Applications
AAP:http://aap.nature-lsa.cn:8080/cms/accessory/files/AAP-lsa201664.pd
Fermionic statistics suppresses Fano resonances
Fano resonances and bound states with energy in the continuum are ubiquitous
phenomena in different areas of physics. Observations, however, have been
limited so far to single-particle processes. In this work we experimentally
investigate the multi-particle case and observe Fano interference in a
non-interacting two-particle Fano-Anderson model by considering propagation of
two-photon states in engineered photonic lattices. We demonstrate that the
quantum statistics of the particles, either bosonic or fermionic, strongly
affects the decay process. Remarkably, we find that the Fano resonance, when
two discrete levels are coupled to a continuum, is suppressed in the fermionic
case
Quantum simulation of bosonic-fermionic non-interacting particles in disordered systems via quantum walk
We report on the theoretical analysis of bosonic and fermionic
non-interacting systems in a discrete two-particle quantum walk affected by
different kinds of disorder. We considered up to 100-step QWs with a spatial,
temporal and space-temporal disorder observing how the randomness and the
wavefunction symmetry non-trivially affect the final spatial probability
distribution, the transport properties and the Shannon entropy of the walkers.Comment: 13 pages, 10 figures. arXiv admin note: text overlap with
arXiv:1101.2638 by other author
Thermally-Reconfigurable Quantum Photonic Circuits at Telecom Wavelength by Femtosecond Laser Micromachining
The importance of integrated quantum photonics in the telecom band resides on
the possibility of interfacing with the optical network infrastructure
developed for classical communications. In this framework, femtosecond laser
written integrated photonic circuits, already assessed for quantum information
experiments in the 800 nm wavelength range, have great potentials. In fact
these circuits, written in glass, can be perfectly mode-matched at telecom
wavelength to the in/out coupling fibers, which is a key requirement for a
low-loss processing node in future quantum optical networks. In addition, for
several applications quantum photonic devices will also need to be dynamically
reconfigurable. Here we experimentally demonstrate the high performance of
femtosecond laser written photonic circuits for quantum experiments in the
telecom band and we show the use of thermal shifters, also fabricated by the
same femtosecond laser, to accurately tune them. State-of-the-art manipulation
of single and two-photon states is demonstrated, with fringe visibilities
greater than 95%. This opens the way to the realization of reconfigurable
quantum photonic circuits on this technological platform
One-dimensional disordered photonic structures with two or more materials
Here we would like to discuss the light transmission modulation by periodic
and disordered one dimensional (1D) photonic structures. In particular, we will
present some theoretical and experimental findings highlighting the peculiar
optical properties of: i) 1D periodic and disordered photonic structures made
with two or more materials; ii) 1D photonic structures in which the homogeneity
or the aggregation of the high refractive index layers is controlled. We will
focus also on the fabrication aspects of these structures.Comment: 6 pages, 4 figure
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