Integrated devices for quantum information with polarization encoded qubits

Integrated devices for quantum information with polarization encoded qubits Dottorato in Fisica XXV ciclo Linda Sansoni Supervisors: Prof. Paolo Mataloni, Dr. Fabio Sciarrino http:\\quantumoptics.phys.uniroma1.it

Quantum information Why polarization encoded qubits

From bulk to integrated optics

My thesis work Ultrafast Laser Writing Integrated devices on glass substrates Polarization encoding Integrated devices Polarization dependent and independent devices Quantum Logic Gates Quantum simulation Quantum transport by quantum walk Ordered systems Static disorder Dynamic disorder Fluctuating disorder Process characterization Quantum process tomography of non trace-preserving maps Variational quantum process tomography

Femtosecond laser writing What about polarization encoding? Laser writing technique for devices able to transmit polarization qubits Femtosecond pulse tightly focused in a glass Combination of multiphoton absorption and avalanche ionization induces permanent and localized refractive index increase in transparent materials Waveguides fabricated in the bulk of the substrate by translating the sample at constant velocity perpendicularly to the laser beam, along the desired path. L. Sansoni et al. Phys. Rev. Lett. 105, 200503 (2010)

Femtosecond laser writing 3-dimensional capabilities Rapid device prototyping: writing speed =4 cm/s Characteristics: Propagation of circular gaussian modes Circular waveguide transverse profile Low birefringence SUITABLE TO SUPPORT ANY POLARIZATION STATE

Optical elements Di ir re ec ct ti io on na al Co ou up pl le er L. Sansoni et al. Phys. Rev. Lett. 105, 200503 (2010) L. Sansoni et al. Phys. Rev. Lett. 108, 010502 (2012) A. Crespi et al. Submitted (2012) A. Crespi et al. Nat. Comm. 2, 566 (2011)

Optical elements Beam Splitter Di ir re ec ct ti io on na al Co ou up pl le er L. Sansoni et al. Phys. Rev. Lett. 105, 200503 (2010) L. Sansoni et al. Phys. Rev. Lett. 108, 010502 (2012) A. Crespi et al. Submitted (2012) A. Crespi et al. Nat. Comm. 2, 566 (2011)

Optical elements Beam Splitter Di ir re ec ct ti io on na al Co ou up pl le er Quantum Walk 3D L. Sansoni et al. Phys. Rev. Lett. 105, 200503 (2010) L. Sansoni et al. Phys. Rev. Lett. 108, 010502 (2012) A. Crespi et al. Submitted (2012) A. Crespi et al. Nat. Comm. 2, 566 (2011)

Beam Splitter Optical elements Di ir re ec ct ti io on na al Coupler Polarizing Beam Splitter Quantum Walk 3D L. Sansoni et al. Phys. Rev. Lett. 105, 200503 (2010) L. Sansoni et al. Phys. Rev. Lett. 108, 010502 (2012) A. Crespi et al. Submitted (2012) A. Crespi et al. Nat. Comm. 2, 566 (2011)

Beam Splitter Optical elements Directional io Coupler Polarizing Beam Splitter Quantum Walk 3D CNOT gate L. Sansoni et al. Phys. Rev. Lett. 105, 200503 (2010) L. Sansoni et al. Phys. Rev. Lett. 108, 010502 (2012) A. Crespi et al. Submitted (2012) A. Crespi et al. Nat. Comm. 2, 566 (2011)

Integrated beam splitter L Polarization entanglement on the chip L: interaction region M. Lobino & J.L. O'Brien News &Views Nature (2011) L. Sansoni et al. Phys. Rev. Lett. 105, 200503 (2010)

Discrete-time quantum walk Quantum walk: extension of the classical random walk: a walker on a lattice jumping between different sites with given probability Classical Quantum

Discrete-time quantum walk Quantum walk: extension of the classical random walk: a walker on a lattice jumping between different sites with given probability Quantum particles evolve on a graph, with their evolution governed by their internal quantum coin (QC) states The walker in the position j is described by the quantum state j> The particle shifts up or down depending on the internal QC state U> or D> Evolution: step operator Experimental platforms Ion trap Fiber loops Coupled waveguides F. Zahringer, et al., Phys. Rev. Lett. 104, 100503 (2010) A. Schreiber et al., Phys. Rev. Lett. 104, 050502 (2010) Phys. Rev. Lett. 106, 180403 (2011) Science 336, 55 (2012) A. Peruzzo, et al., Science 329, 1500 (2010) JCF Matthews, et al., ArXiv:1106.1166 (2011)

Why Quantum Walk Walk Energy transfer: within photosynthetic systems can display quantum effects such as delocalized excitonic transport which can be simulated by QW. Controlled transition from Classical to Quantum: QW can be employed for testing the transition from the quantum to the classical world by applying a controlled degree of decoherence. Light-harvesting molecule: is efficient at concentrating light at its center as quantum walk reaches the target vertex exponentially faster than a classical walk: because of destructive interference between the paths that point backward, toward the leaves. QW? Faster quantum Computation: It has been theoretically proven that Qws allow the speed-up of search algorithms

Photonic implementation of quantum walks Single photons Beam splitters Phase shifters Photodetectors

Photonic implementation of quantum walks Single photons Beam splitters Phase shifters Photodetectors QW SITES STEPS

Two-particle quantum walk The symmetry of two travelling quantum walkers influences the output probability distribution Polarization independent integrated beam splitter Exploit polarization entanglement to change the symmetry of two-particle wavefunction

Simulation of ordered & disordered systems

Simulation of ordered & disordered systems Position dependent disorder Anderson localization

Simulation of disordered systems: two-particle quantum walk Experimental Setup L. Sansoni, et al., Phys. Rev. Lett. 108, 010502 (2012) A. Crespi, et al., Submitted (2012)

Ordered vs Static Quantum Walk: Single-particle Ordered systems Disordered systems Experiment Observed experimentally by Silberhorn's group with fiber loops: Physical Review Letters 106, 180403 (2011). Two-particle quantum walk with disordered systems: experiments missing so far... Theoretical investigation by Silberberg's group Y. Lahini, et al., Physical Review Letters 105, 163905 (2010).

Ordered vs Static Quantum Walk: Experimental results L. Sansoni, et al., Phys. Rev. Lett. 108, 010502 (2012) A. Crespi, et al., Submitted (2012)

Conclusions and perspectives Integrated devices Quantum simulation Polarization independent Polarization dependent Ordered systems Disordered systems Beam Splitter CNOT L. Sansoni et al. Phys. Rev. Lett. 105, 200503 (2010) A. Crespi, et al., Nat. Comm. 2, 566 (2011) L. Sansoni et al. Phys. Rev. Lett. 108, 010502 (2012) A. Crespi, et al., Submitted (2012) Process characterization I. Bongioanni et al. Phys. Rev. A 82, 042307 (2010) R.O. Vianna, et al., Submitted (2012)

Publications PhD L. Sansoni et al. Phys. Rev. Lett. 105, 200503 (2010) I. Bongioanni et al. Phys. Rev. A 82, 042307 (2010) A. Crespi et al. Nature Communication 2, 566 (2011) L. Sansoni et al. Phys. Rev. Lett. 108, 010502 (2012) A. Crespi, et al. Submitted (2012) R. O. Vianna et al. Submitted (2012) Conferences Schools QNLO 2010, Quantum and Nonlinear Optics, Sandjberg (Denmark) 22-28 August 2010, poster presentation. SUSSP67 Quantum Information and Coherence, Glasgow (Scotland) 28 July- 10August 2011, poster presentation (Won best poster award) QuAMP 2012 Quantum Atomic, Molecular and Plasma Physics, Belfast (UK) 9-13 September 2012, oral and poster presentations 453. WE-Heraeus Seminar, Quantum Communication Based on Integrated Optics, Bad Honnef (Germany) 22-25 March 2010, poster presentation: Fotonica 2010, Pisa (Italy) 25-27 May 2010, oral presentation SPIE Optics+Optoelectronics, Prague (Czech Republic) 18-21 April 2011, oral presentation CLEO2011 Lasers for photonic applications, Baltimore (Mariland USA) 1-6 May 2011, oral presentation SPIE Photonics Europe, Brussels (Belgium) 16-19 April 2012, oral presentation Conference on Disordered Quantum Systems, Paris (France) 18-22 June 2012, poster presentation LPHYS'12 International Laser Physics Workshop, Calgary (Canada) 23-27 July 2012, invited talk XCVIII Congresso Nazionale SIF-Società Italiana di Fisica, Naples (Italy) 17-21 September 2012, oral presentation