scholarly journals Self-error-corrected hyperparallel photonic quantum computation working with both the polarization and the spatial-mode degrees of freedom

2018 ◽  
Vol 26 (18) ◽  
pp. 23333 ◽  
Author(s):  
Guan-Yu Wang ◽  
Tao Li ◽  
Qing Ai ◽  
Fu-Guo Deng
Keyword(s):  
Quantum Computation ◽  
Degrees Of Freedom ◽  
Spatial Mode ◽  
Photonic Quantum Computation

scholarly journals High-Dimensional Pixel Entanglement: Efficient Generation and Certification

Quantum ◽  
2020 ◽  
Vol 4 ◽  
pp. 376
Author(s):  
Natalia Herrera Valencia ◽  
Vatshal Srivastav ◽  
Matej Pivoluska ◽  
Marcus Huber ◽  
Nicolai Friis ◽  
...  
Keyword(s):  
Carrying Capacity ◽  
Communication Systems ◽  
Degrees Of Freedom ◽  
State Of The Art ◽  
Quality Measurement ◽  
High Dimensional ◽  
Single Photons ◽  
Spatial Mode ◽  
Classical Communication ◽  
Entanglement Of Formation

Photons offer the potential to carry large amounts of information in their spectral, spatial, and polarisation degrees of freedom. While state-of-the-art classical communication systems routinely aim to maximize this information-carrying capacity via wavelength and spatial-mode division multiplexing, quantum systems based on multi-mode entanglement usually suffer from low state quality, long measurement times, and limited encoding capacity. At the same time, entanglement certification methods often rely on assumptions that compromise security. Here we show the certification of photonic high-dimensional entanglement in the transverse position-momentum degree-of-freedom with a record quality, measurement speed, and entanglement dimensionality, without making any assumptions about the state or channels. Using a tailored macro-pixel basis, precise spatial-mode measurements, and a modified entanglement witness, we demonstrate state fidelities of up to 94.4% in a 19-dimensional state-space, entanglement in up to 55 local dimensions, and an entanglement-of-formation of up to 4 ebits. Furthermore, our measurement times show an improvement of more than two orders of magnitude over previous state-of-the-art demonstrations. Our results pave the way for noise-robust quantum networks that saturate the information-carrying capacity of single photons.

Cluster state quantum computation for many-level systems

2007 ◽  
Vol 7 (3) ◽  
pp. 184-208
Author(s):  
W. Hall
Keyword(s):  
Quantum Computation ◽  
Degrees Of Freedom ◽  
Cluster State ◽  
Quantum Systems ◽  
Explicit Description ◽  
State Model ◽  
Mutually Unbiased Bases ◽  
Large Set ◽  
Adaptive Computation ◽  
Complete Framework

The cluster state model for quantum computation [Phys. Rev. Lett. \textbf{86}, 5188] outlines a scheme that allows one to use measurement on a large set of entangled quantum systems in what is known as a cluster state to undertake quantum computations. The model itself and many works dedicated to it involve using entangled qubits. In this paper we consider the issue of using entangled qudits instead. We present a complete framework for cluster state quantum computation using qudits, which not only contains the features of the original qubit model but also contains the new idea of adaptive computation: via a change in the classical computation that helps to correct the errors that are inherent in the model, the implemented quantum computation can be changed. This feature arises through the extra degrees of freedom that appear when using qudits. Finally, for prime dimensions, we give a very explicit description of the model, making use of mutually unbiased bases.

scholarly journals Multidimensional entanglement transport through single-mode fiber

2020 ◽  
Vol 6 (4) ◽  
pp. eaay0837 ◽  
Author(s):  
Jun Liu ◽  
Isaac Nape ◽  
Qainke Wang ◽  
Adam Vallés ◽  
Jian Wang ◽  
...  
Keyword(s):  
Hilbert Spaces ◽  
Mode Coupling ◽  
Degrees Of Freedom ◽  
Single Mode ◽  
Single Mode Fiber ◽  
Entangled States ◽  
Spatial Mode ◽  
Alternative Approach ◽  
Spatial Modes ◽  
State Tomography

The global quantum network requires the distribution of entangled states over long distances, with substantial advances already demonstrated using polarization. While Hilbert spaces with higher dimensionality, e.g., spatial modes of light, allow higher information capacity per photon, such spatial mode entanglement transport requires custom multimode fiber and is limited by decoherence-induced mode coupling. Here, we circumvent this by transporting multidimensional entangled states down conventional single-mode fiber (SMF). By entangling the spin-orbit degrees of freedom of a biphoton pair, passing the polarization (spin) photon down the SMF while accessing multiple orbital angular momentum (orbital) subspaces with the other, we realize multidimensional entanglement transport. We show high-fidelity hybrid entanglement preservation down 250 m SMF across multiple 2 × 2 dimensions, confirmed by quantum state tomography, Bell violation measures, and a quantum eraser scheme. This work offers an alternative approach to spatial mode entanglement transport that facilitates deployment in legacy networks across conventional fiber.

scholarly journals Digital toolbox for vector field characterization

Nanophotonics ◽  
2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Keshaan Singh ◽  
Angela Dudley
Keyword(s):  
Vector Field ◽  
Laser Cutting ◽  
Degrees Of Freedom ◽  
Automated Measurement ◽  
Spatial Mode ◽  
Quantum Channels ◽  
Correlation Filters ◽  
Equal Importance ◽  
Polarization Optics ◽  
Projective Measurements

Abstract Vectorial structured light fields have displayed properties advantageous in many disciplines ranging from communications, microscopy and metrology to laser cutting and characterizing quantum channels. The generation of these fields has been made convenient through the implementation of nanophotonic metasurfaces amongst other static and digital techniques. Consequently, the detection and characterisation of these fields is of equal importance. Most existing techniques involve using separate polarization optics and correlation filters to perform the projective measurements – or are only able to perform such measurements on a subset of possible vector states. We present a compact, fully automated measurement technique based on a digital micro-mirror device (DMD), which facilitates the complete, local and global, characterisation of the spatial mode and polarization degrees-of-freedom (DOFs) for arbitrary vectorial fields. We demonstrate our approach through the identification of relevant hybrid-order Poincaré spheres, the reconstruction of state vectors on these spheres, as well as the recovery of the non-separability and states-of-polarization for a variety of vector beams.

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