Quantum computation and simulation with photons

Lunedi' 17 Gennaio 2011 - Giuseppe Vallone

ARGOMENTI: International Area

Il giorno Lunedi' 17 Gennaio 2011 alle ore 15:00 in Aula Magna "A. Lepschy" - DEI - via Gradenigo 6 - Padova, il Dr. Giuseppe Vallone (Dipartimento di Fisica, Università di Roma La Sapienza) terra' una conferenza dal titolo "Quantum computation and simulation with photons".

Using the laws of quantum mechanics for computation may lead to larger advantages for the resolution of extremely complex problems. For instance, a quantum computer exhibits larger computational power with respect to classical one. Quantum optics represents an excellent experimental test bench for several fundamental concepts introduced within the framework of quantum information (QI) theory. The creation and manipulation of entanglement, a unique resource characterized by correlations between different systems not allowed in the classical world, is a key ingredient for QI. We present the production a new family of multipartite entangled states realized with two photons and we experimentally simulate the presence of noise. We then tested the robustness properties of the states. We will also present the realization of the Deutsch-Jozsa (DJ) algorithm able to discriminate in a single run between constant and balanced n-bit functions. For a 2-bit function we used a two-photon six-qubit state. The presented experiments represent useful and necessary proof of principles but suffer from bulk optic limitations: low phase stability and large physical dimension. The emerging strategy to overcome these limitations and to move forward applications outside laboratory consists of taking advantage of the robustness and compactness achievable by integrated waveguide technology. We report the realization of a directional coupler, fabricated by femtosecond laser waveguide writing, acting as an integrated beam splitter able to support polarization-encoded information. Using this device, we demonstrate quantum interference with polarization-entangled states and singlet state projection.