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Arbitrary photonic wave plate operations on chip: realizing Hadamard, Pauli-X, and rotation gates for polarisation qubits.

Heilmann R, Gräfe M, Nolte S, Szameit A - Sci Rep (2014)

Bottom Line: By adjusting this length of the defect along the waveguide, the retardation between ordinary and extraordinary field components is precisely tunable including half-wave plate and quarter-wave plate operations.Our approach demonstrates the full range control of orientation and strength of the induced birefringence and thus allows arbitrary wave plate operations without affecting the degree of polarisation or introducing additional losses to the waveguides.The implemented gates are tested with classical and quantum light.

View Article: PubMed Central - PubMed

Affiliation: Institute of Applied Physics, Abbe Center of Photonics, Friedrich-Schiller-Universität Jena, Max-Wien-Platz 1, 07743 Jena, Germany.

ABSTRACT
Chip-based photonic quantum computing is an emerging technology that promises much speedup over conventional computers at small integration volumes. Particular interest is thereby given to polarisation-encoded photonic qubits, and many protocols have been developed for this encoding. However, arbitrary wave plate operation on chip are not available so far, preventing from the implementation of integrated universal quantum computing algorithms. In our work we close this gap and present Hadamard, Pauli-X, and rotation gates of high fidelity for photonic polarisation qubits on chip by employing a reorientation of the optical axis of birefringent waveguides. The optical axis of the birefringent waveguide is rotated due to the impact of an artificial stress field created by an additional modification close to the waveguide. By adjusting this length of the defect along the waveguide, the retardation between ordinary and extraordinary field components is precisely tunable including half-wave plate and quarter-wave plate operations. Our approach demonstrates the full range control of orientation and strength of the induced birefringence and thus allows arbitrary wave plate operations without affecting the degree of polarisation or introducing additional losses to the waveguides. The implemented gates are tested with classical and quantum light.

No MeSH data available.


Related in: MedlinePlus

Settings.(a) Idealised schematic showing the cross section of the waveguide arrangement where additional stress fields induce a reorientation of the waveguide's optical axis. (b) Sketch of the writing setting, with which the quantum gates are fabricated (here for 3 different orientations of the defect relatively to the waveguide). Higher pulse energies and lower writing velocity for the defects causes their missing light guiding properties and, hence, prevent loss due to coupling.
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f1: Settings.(a) Idealised schematic showing the cross section of the waveguide arrangement where additional stress fields induce a reorientation of the waveguide's optical axis. (b) Sketch of the writing setting, with which the quantum gates are fabricated (here for 3 different orientations of the defect relatively to the waveguide). Higher pulse energies and lower writing velocity for the defects causes their missing light guiding properties and, hence, prevent loss due to coupling.

Mentions: Our experimental analysis of this phenomenon delivers the surprising result that, when an additional waveguide is prone to such a stress field, an artificial birefringence is induced in this guide, which results in a reorientation of the optical axis as a function of the relative position of the two guides. As the relative position (in distance and angle) can be tuned with high precision, strong tilting of the birefringent axis can be implemented at will, allowing arbitrary desired wave plate operations on the light that propagates in the waveguide exposed to the stress field. A sketch of this effect is shown in Fig. 1(a). To prevent the system from coupling light to the defect, the defect is written slightly above the destruction threshold. The main advantage of our approach is that the original waveguide shape remains unchanged irrespective of the optical axis' orientation that causes the wave plate operation. Hence, there is no additional friction of the propagating light caused by the artificial birefringence The additional losses in presence of the defect are <0.01 dB/cm.


Arbitrary photonic wave plate operations on chip: realizing Hadamard, Pauli-X, and rotation gates for polarisation qubits.

Heilmann R, Gräfe M, Nolte S, Szameit A - Sci Rep (2014)

Settings.(a) Idealised schematic showing the cross section of the waveguide arrangement where additional stress fields induce a reorientation of the waveguide's optical axis. (b) Sketch of the writing setting, with which the quantum gates are fabricated (here for 3 different orientations of the defect relatively to the waveguide). Higher pulse energies and lower writing velocity for the defects causes their missing light guiding properties and, hence, prevent loss due to coupling.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3927208&req=5

f1: Settings.(a) Idealised schematic showing the cross section of the waveguide arrangement where additional stress fields induce a reorientation of the waveguide's optical axis. (b) Sketch of the writing setting, with which the quantum gates are fabricated (here for 3 different orientations of the defect relatively to the waveguide). Higher pulse energies and lower writing velocity for the defects causes their missing light guiding properties and, hence, prevent loss due to coupling.
Mentions: Our experimental analysis of this phenomenon delivers the surprising result that, when an additional waveguide is prone to such a stress field, an artificial birefringence is induced in this guide, which results in a reorientation of the optical axis as a function of the relative position of the two guides. As the relative position (in distance and angle) can be tuned with high precision, strong tilting of the birefringent axis can be implemented at will, allowing arbitrary desired wave plate operations on the light that propagates in the waveguide exposed to the stress field. A sketch of this effect is shown in Fig. 1(a). To prevent the system from coupling light to the defect, the defect is written slightly above the destruction threshold. The main advantage of our approach is that the original waveguide shape remains unchanged irrespective of the optical axis' orientation that causes the wave plate operation. Hence, there is no additional friction of the propagating light caused by the artificial birefringence The additional losses in presence of the defect are <0.01 dB/cm.

Bottom Line: By adjusting this length of the defect along the waveguide, the retardation between ordinary and extraordinary field components is precisely tunable including half-wave plate and quarter-wave plate operations.Our approach demonstrates the full range control of orientation and strength of the induced birefringence and thus allows arbitrary wave plate operations without affecting the degree of polarisation or introducing additional losses to the waveguides.The implemented gates are tested with classical and quantum light.

View Article: PubMed Central - PubMed

Affiliation: Institute of Applied Physics, Abbe Center of Photonics, Friedrich-Schiller-Universität Jena, Max-Wien-Platz 1, 07743 Jena, Germany.

ABSTRACT
Chip-based photonic quantum computing is an emerging technology that promises much speedup over conventional computers at small integration volumes. Particular interest is thereby given to polarisation-encoded photonic qubits, and many protocols have been developed for this encoding. However, arbitrary wave plate operation on chip are not available so far, preventing from the implementation of integrated universal quantum computing algorithms. In our work we close this gap and present Hadamard, Pauli-X, and rotation gates of high fidelity for photonic polarisation qubits on chip by employing a reorientation of the optical axis of birefringent waveguides. The optical axis of the birefringent waveguide is rotated due to the impact of an artificial stress field created by an additional modification close to the waveguide. By adjusting this length of the defect along the waveguide, the retardation between ordinary and extraordinary field components is precisely tunable including half-wave plate and quarter-wave plate operations. Our approach demonstrates the full range control of orientation and strength of the induced birefringence and thus allows arbitrary wave plate operations without affecting the degree of polarisation or introducing additional losses to the waveguides. The implemented gates are tested with classical and quantum light.

No MeSH data available.


Related in: MedlinePlus