Philip Intallura Ph.D

Monte Carlo sampling is a powerful toolbox of algorithmic techniques widely used for a number of applications wherein some noisy quantity, or summary statistic thereof, is sought to be estimated. In this paper, we survey the literature for implementing Monte Carlo procedures using quantum circuits, focusing on the potential to obtain a quantum advantage in the computational speed of these procedures. We revisit the quantum algorithms that could replace classical Monte Carlo and then consider… Show more

Monte Carlo sampling is a powerful toolbox of algorithmic techniques widely used for a number of applications wherein some noisy quantity, or summary statistic thereof, is sought to be estimated. In this paper, we survey the literature for implementing Monte Carlo procedures using quantum circuits, focusing on the potential to obtain a quantum advantage in the computational speed of these procedures. We revisit the quantum algorithms that could replace classical Monte Carlo and then consider both the existing quantum algorithms and the potential quantum realizations that include adaptive enhancements as alternatives to the classical procedure. Show less

Encoding classical data on quantum spin Hamiltonians yields ordered spin ground states which are used to discriminate data types for binary classification. The Ising Hamiltonian is a typical spin model to encode classical data onto qubits, known as the ZZ feature map. We assess the ground states of the Ising Hamiltonian encoded with three separate data sets containing two classes of data. A new methodology is proposed to predict a certain data class using the ground state of the encoded Ising… Show more

Encoding classical data on quantum spin Hamiltonians yields ordered spin ground states which are used to discriminate data types for binary classification. The Ising Hamiltonian is a typical spin model to encode classical data onto qubits, known as the ZZ feature map. We assess the ground states of the Ising Hamiltonian encoded with three separate data sets containing two classes of data. A new methodology is proposed to predict a certain data class using the ground state of the encoded Ising Hamiltonian. Ground state observables are obtained through quantum simulation on a quantum computer, and the expectation values are used to construct a classical probability distribution on the state space. Our approach is a low dimensional representation of the exponentially large feature space. The antiferromagnetic ground state is the stable ground state for the one dimensional chain lattice and the 2D square lattice. Frustration induces unique ordered states on the triangle lattice encoded with data, hinting at the possibility for an underlying phase diagram for the model. We examine order stability with data scaling and data noise. Show less

We report on polarisation correlation from the cascaded recombination of biexcitons in a quantum dot emitting at a telecommunication wavelength. The fine structure splitting of the exciton state in this InAs/GaAs quantum dot is of the order of 100 μeV and polarisation correlation is expected. Strong polarisation correlation between the biexciton and exciton emission lines is observed under both continuous wave (CW) and pulsed laser excitation so telecom wavelength quantum dots with lower energy… Show more

We report on polarisation correlation from the cascaded recombination of biexcitons in a quantum dot emitting at a telecommunication wavelength. The fine structure splitting of the exciton state in this InAs/GaAs quantum dot is of the order of 100 μeV and polarisation correlation is expected. Strong polarisation correlation between the biexciton and exciton emission lines is observed under both continuous wave (CW) and pulsed laser excitation so telecom wavelength quantum dots with lower energy splittings could be suitable for entangled photon pair generation. Measurements were performed using nanowire superconducting single photon detectors (SSPDs). SSPDs offer low time-jitter and improve the resolution of features in the correlation spectra, including the asymmetric dip and peak resulting from the cascaded emission with the peak extending more than an order of magnitude above the Poissonian level. Show less

Quantum key distribution with single photons from a telecommunication-wavelength quantum dot source is performed over a standard optical fibre link. The source was operated at a temperature of 70 K and gave g(2)(0)~0.166 with an efficiency of 5% after coupling into the single-mode fibre. Correlation results are quoted without subtraction of detector dark counts and g(2)(0) as low as 0.1 was measured, at reduced efficiency. This source enabled a proof-of-principle demonstration of quantum key… Show more

Quantum key distribution with single photons from a telecommunication-wavelength quantum dot source is performed over a standard optical fibre link. The source was operated at a temperature of 70 K and gave g(2)(0)~0.166 with an efficiency of 5% after coupling into the single-mode fibre. Correlation results are quoted without subtraction of detector dark counts and g(2)(0) as low as 0.1 was measured, at reduced efficiency. This source enabled a proof-of-principle demonstration of quantum key distribution over 35 km of fibre using the BB84 protocol and phase encoding. Show less

We present the first demonstration of telecom fiber-based quantum key distribution using single photons from a quantum dot in a pillar microcavity. The source offers both telecommunication wavelength operation at 1.3 microns and Purcell enhancement of the spontaneous emission rate. Several emission lines from the InAs/GaAs quantum dot are identified, including the exciton-biexciton cascade and charged excitonic emission. We show an order of magnitude increase in the collected intensity of the… Show more

We present the first demonstration of telecom fiber-based quantum key distribution using single photons from a quantum dot in a pillar microcavity. The source offers both telecommunication wavelength operation at 1.3 microns and Purcell enhancement of the spontaneous emission rate. Several emission lines from the InAs/GaAs quantum dot are identified, including the exciton-biexciton cascade and charged excitonic emission. We show an order of magnitude increase in the collected intensity of the emission from a charged excitonic state when temperature tuned onto resonance with the HE11 mode of the pillar microcavity, as compared to the off-resonance intensity. Above- and below-GaAs-bandgap optical excitation was used and the effect of the excitation energy on the photoluminescence investigated. Exciting below the GaAs-bandgap offers significant improvement in the quality of the single photon emission and a reduction of the multi-photon probability to 0.1 times the value for Poissonian light was measured, before subtraction of detector dark counts, the lowest value recorded to date for a quantum dot source at a fibre wavelength. We observe also the first evidence of Purcell enhancement of the spontaneous emission rate for a single telecommunication wavelength quantum dot in a pillar microcavity. We have incorporated the source into a phase encoded interferometric scheme implementing the BB84 quantum cryptography protocol and distributed a key, secure from the pulse splitting attack, over standard telecommunication optical fibre. We show a transmission distance advantage over that possible with (length-optimized) uniform intensity weak coherent pulses at 1310 nm in the same system. Show less

We report the distribution of a cryptographic key, secure from photon number splitting attacks, over 35km of optical fiber using single photons from an InAs quantum dot emitting ∼ 1.3μm in a pillar microcavity. Using below GaAs-bandgap optical excitation, we demonstrate suppression of multiphoton emission to 10% of the Poissonian level without detector dark count subtraction. The source is incorporated into a phase encoded interferometric scheme implementing the BB84 protocol for key… Show more

We report the distribution of a cryptographic key, secure from photon number splitting attacks, over 35km of optical fiber using single photons from an InAs quantum dot emitting ∼ 1.3μm in a pillar microcavity. Using below GaAs-bandgap optical excitation, we demonstrate suppression of multiphoton emission to 10% of the Poissonian level without detector dark count subtraction. The source is incorporated into a phase encoded interferometric scheme implementing the BB84 protocol for key distribution over standard telecommunication optical fiber. We show a transmission distance advantage over that possible with (length-optimized) uniform intensity weak coherent pulses at 1310 nm in the same system. Show less