arXiv subjects

Pavel Trojek

Publications and source records attributed to Pavel Trojek.

5 recordsLinked to original sources

arXiv2012

A high-brightness source of polarization-entangled photons optimized for applications in free space

We present a simple but highly efficient source of polarization-entangled photons based on spontaneous parametric down-conversion (SPDC) in bulk periodically poled potassium titanyl phosphate crystals (PPKTP) pumped by a 405 nm laser diode. Utilizing one of the highest available nonlinear coefficients in a non-degenerate, collinear type-0 phase-matching configuration, we generate polarization entanglement via the crossed-crystal scheme and detect 0.64 million photon pair events/s/mW, while maintaining an overlap fidelity with the ideal Bell state of 0.98 at a pump power of 0.025 mW.

quant-ph↗

arXiv2008

Collinear source of polarization-entangled photon pairs at non-degenerate wavelengths

We report on a simple but highly efficient source of polarization-entangled photon pairs at non-degenerate wavelengths. The fully collinear configuration of the source enables very high coupling efficiency into a single optical mode and allows the use of long nonlinear crystals. With optimized dispersion compensation it is possible to use a free-running laser diode as pump source and to reach an entanglement fidelity of 99.4 % at rates as high as 27000 pairs/s per mW of pump power. This greatly enhances the practicality of the source for applications in quantum communication and metrology.

quant-ph↗

arXiv2005

Single Qubit Quantum Secret Sharing

We present a simple and practical protocol for the solution of a secure multiparty communication task, the secret sharing, and its experimental realization. In this protocol, a secret message is split among several parties in a way that its reconstruction require the collaboration of the participating parties. In the proposed scheme the parties solve the problem by a sequential communication of a single qubit. Moreover we show that our scheme is equivalent to the use of a multiparty entangled GHZ state but easier to realize and better scalable in practical applications.

quant-ph↗

arXiv2005

Experimental quantum communication complexity

We prove that the fidelity of two exemplary communication complexity protocols, allowing for an N-1 bit communication, can be exponentially improved by N-1 (unentangled) qubit communication. Taking into account, for a fair comparison, all inefficiencies of state-of-the-art set-up, the experimental implementation outperforms the best classical protocol, making it the candidate for multi-party quantum communication applications.

quant-ph↗

arXiv2003

Experimental verification of energy correlations in entangled photon pairs

Properties of entangled photon pairs generated in spontaneous parametric down-conversion are investigated in interference experiments. Strong energy correlations are demonstrated in a direct way. If a signal photon is detected behind a narrow spectral filter, then interference appears in the Mach-Zehnder interferometer placed in the route of the idler photon, even if the path difference in the interferometer exceeds the coherence length of the light. Narrow time correlations of the detection instants are demonstrated for the same photon-pair source using the Hong-Ou-Mandel interferometer. Both these two effects may be exhibited only by an entangled state.

quant-ph↗