arXiv subjects

Andrea Fiore

Publications and source records attributed to Andrea Fiore.

25 records · Page 2Linked to original sources

arXiv2012

Widely tunable, efficient on-chip single photon sources at telecommunication wavelengths

We demonstrate tunable on-chip single photon sources using the Stark tuning of single quantum dot (QD) excitonic transitions in short photonic crystal waveguides (PhC WGs). The emission of single QDs can be tuned in real-time by 9 nm with an applied bias voltage less than 2V. Due to a reshaped density of optical modes in the PhC WG, a large coupling efficiency β>65% to the waveguide mode is maintained across a wavelength range of 5 nm. When the QD is resonant with the Fabry-Perot mode of the PhC WG, a strong enhancement of spontaneous emission is observed leading to a maximum coupling efficiency β=88%. These results represent an important step towards the scalable integration of single photon sources in quantum photonic integrated circuits.

cond-mat.mes-hall↗

arXiv2012

Proposal of a two-qubit quantum phase gate for quantum photonic integrated circuits

We propose a protocol for two-qubit quantum phase gate based upon reflection of photon pulses from a quantum dot in a cavity. Depending on the state of the quantum dot the reflected photons acquire a conditional phase shift. The key ingredient is the ultrafast control of the quantum dot energies by electric fields, which allows for tuning the exciton and biexciton successively into resonance with the cavity mode. The complete dynamics of the gate are simulated revealing a fidelity of about 0.9. The proposed scheme uses position-coding and is therefore well suited to the implementation in an integrated photonic quantum processor.

quant-ph↗

arXiv2012

Photon-number resolving detector based on a series array of superconducting nanowires

We present the experimental demonstration of a superconducting photon number resolving detector. It is based on the series connection of N superconducting nanowires, each connected in parallel to an integrated resistor. The device provides a single voltage readout, proportional to the number of photons absorbed in distinct nanowires. Clearly separated output levels corresponding to the detection of n=1-4 photons are observed in a 4-element detector fabricated from an NbN film on GaAs substrate, with a single-photon system quantum efficiency of 2.6% at the wavelength of 1300nm. The series-nanowire structure is promising in view of its scalability to large photon numbers and high efficiencies.

physics.ins-det↗

arXiv2012

Enhanced spontaneous emission from quantum dots in short photonic crystal waveguides

We report a study of the quantum dot emission in short photonic crystal waveguides. We observe that the quantum dot photoluminescence intensity and decay rate are strongly enhanced when the emission energy is in resonance with Fabry-Perot cavity modes in the slow-light regime of the dispersion curve. The experimental results are in agreement with previous theoretical predictions and further supported by three-dimensional finite element simulation. Our results show that the combination of slow group velocity and Fabry-Perot cavity resonance provides an avenue to efficiently channel photons from quantum dots into waveguides for integrated quantum photonic applications.

physics.optics↗

arXiv2011

Single photon absorption and dynamic control of a coupled quantum dot-cavity system

We theoretically investigate the dynamic interaction of a quantum dot in a nanocavity with timesymmetric single photon pulses. The simulations, based on a wavefunction approach, reveal that almost perfect single photon absorption occurs for quantum dot-cavity systems operating on the edge between strong and weak coupling regime. The computed maximum absorptions probability is close to unity for pulses with a typical length comparable to the half of the Rabi period. Furthermore, the dynamic control of the quantum dot energy via electric fields allows the freezing of the light-matter interaction leaving the quantum dot in its excited state. Shaping of single photon wavepackets by the electric field control is limited by the occurrence of chirping of the single photon pulse. This understanding of the interaction of single photon pulses with the quantum dot-cavity system provides the basis for the development of advanced protocols for quantum information processing in the solid state.

quant-ph↗

arXiv2010

Nanoscale single- and multi-photon mapping of optical fields

The study of optical phenomena on the subwavelength scale is becoming increasingly important in photonics, particularly in the fields of nanoemitters, photonic crystals and plasmonics. Subwavelength field patterns are evanescent and must thus be investigated with near-field techniques. The light powers emitted by nanoscale sources are extremely low, undermining the traditional approach of scattering a near field to a large (thus noisy) far-field detector. Nanoscale detectors, providing direct sensing in the near-field with small noise due to a small active area, are needed in high-sensitivity, high-resolution near-field imaging and in quantum nanophotonic circuits. Here we report the first nanoscale ~50x50nm2) detector displaying single-photon sensitivity and a nanosecond response. These nanodetectors can also be operated in multi-photon mode, where the detection threshold can be set at N=1, 2, 3 or 4 photons, thus allowing the mapping of photon number statistics on the nanoscale.

physics.optics↗

arXiv2007

Superconducting nanowire photon number resolving detector at telecom wavelength

The optical-to-electrical conversion, which is the basis of optical detectors, can be linear or nonlinear. When high sensitivities are needed single-photon detectors (SPDs) are used, which operate in a strongly nonlinear mode, their response being independent of the photon number. Nevertheless, photon-number resolving (PNR) detectors are needed, particularly in quantum optics, where n-photon states are routinely produced. In quantum communication, the PNR functionality is key to many protocols for establishing, swapping and measuring entanglement, and can be used to detect photon-number-splitting attacks. A linear detector with single-photon sensitivity can also be used for measuring a temporal waveform at extremely low light levels, e.g. in long-distance optical communications, fluorescence spectroscopy, optical time-domain reflectometry. We demonstrate here a PNR detector based on parallel superconducting nanowires and capable of counting up to 4 photons at telecommunication wavelengths, with ultralow dark count rate and high counting frequency.

physics.optics↗