Our goal in the Centre for Quantum Photonics is to explore fundamental aspects of quantum mechanics, as well as work towards future photonic quantum technologies by generating, manipulating and measuring single photons as well as the quantum systems that emit these photons, with a focus on scalable integrated optics devices.
Lead by Prof. Jeremy O'Brien, the Centre spans the School of Physics, Department of Electrical and Electronic Engineering, and the Centre for Nanoscience and Quantum Information, at the University of Bristol, UK.
Our group performs researches, both experimental and theoretical, devoted to the investigation of entanglement in quantum mechanics and its application to quantum technologies, as quantum information processing and quantum metrology.
More in detail, many experiments based on the use of entangled pairs of photons have been performed, or are on realisation, using the eight laboratories of "Carlo Novero lab" (devoted to the memory of Carlo Novero who began this activity at IEN). Among them:
1. We have realised some experiments concerning Foundations of Quantum Mechanics. In particular, a test of Bell inequalities using the superposition of two type I PDC emissions, that allowed the generation of non-maximally entangled states. This experiment allowed a progress toward a conclusive test of local realism and permitted to exclude some specific hidden variable theory. Furthermore, some experiments were addressed to test some other specific realistic models. We also performed experiments aiming the investigation on the bounds of quantum correlation. Finally, an experiment on wave-particle duality was realised with various optical states as well. This activity has been done in part in collaboration with Turin University.
2. We contributed to the realization of the first Italian prototype of entanglement based quantum cryptography link in the framework of a national research program leaded by ELSAGDATAMAT. In this context we investigated both theoretically and experimentally quantum key distribution, and quantum secure direct communication protocols based on entangled photon pairs. We realised QKD protocols based on orthogonal states (Goldberg-Vaidman's and controfactual ones) and the controfactual one. At the moment, we are studying both quantum communication channel (fiber/open air) effects and the realisation of innovative protocols. We participate to ETSI work group on standardisation of QKD.
3. Absolute photodetectors calibration using correlated photons. Beyond studies on the traditional PDC scheme, an innovative method, based on a measurement conditional unitary gate on qubit (photon polarisation), has been developed in collaboration with Moscow University. More recently researches were performed for calibrating analog detectors.
4. Realisation and characterisation of PDC sources with specific properties, also realized in microstructured materals (such as PPLN crystals and waveguides) and study of entanglement coupling and propagation in fiber. We are also studying entanglement measures of PDC biphotons.
5. Studies and realisations of prototypes of single photon detection system with reduced deadtime exploiting multiplexing based on active optical switch (in collaboration with NIST). Characterisation of TES detectors (in collaboration with Milan University).
6. Studies on reconstruction of photon statistic and, more recently, of the full density matrix by using on/off detectors were performed in collaboration with Milan and Insubria Universities. Study on optimality of tomographic protocols and tomography of POVM.
7. We performed studies on the connection between Quantum Imaging and entanglement. We have realised for the first time a Sub-Shot-Noise Quantum Imaging experiment. These activities are performed in collaboration with Insubria and Milan Universities.
8. From a theoretical side we worked on multidimensional QKD and studied application of mesons to local realism tests.
ICMM, International center for Mathematical Modeling
in physics, engineering and cognitive sciences
Directions of research at the ICMM :
<ul><li>Mathematical methods of quantum physics (field theory, Feynman integrals, supersymmetric fields, structure of space-time on Planck distances).</li>
<li>Quantum computers and teleportation.</li>
<li>Acoustics and theory of partial differential equations (with applications to auto and air-plane modeling).</li>
<li>Electromagnetic fields and partial differential equations (with applications to radio and television signals).</li>
<li>Chaotic systems in classical and quantum physics (with applications to electrical engineering and cognitive sciences).</li>
<li>Cognitive information models and neural networks (with applications to sociology and brain's functioning).</li>
<li>Cognitive information models and quantum physics (with applications to sociology).</li>
<li>Image analysis and compression of information (for radio and television signals).</li>
<li>Fluid dynamics applied to fans and transport.</li>
<li>Mathematical models in economy, especially migration models.</li>
<li>Financial mathematics with specialization for the Swedish stock market.</li>
<li>Wood project (physical and mathematical problems). </li></ul>
Quantum computation (QC) holds out tremendous promise for efficiently solving some of the most difficult problems in computational science, such as integer factorization, discrete logarithms, and quantum modeling that are intractable on any present or future conventional computer. In addition, quantum cryptography(QKD) is considered the most powerful data encryption scheme ever developed and its codes are, by all indications, virtually unbreakable. At LANL, we are currently developing new concepts for QKD and QC implementations, advancing our theoretical and experimental understanding of the physics requirements for quantum information processing.