dorsal/arxiv
View SchemaExperimental implementation of time-coding quantum key distribution
| Authors | William Boucher, Thierry Debuisschert |
|---|---|
| Categories | |
| ArXiv ID | quant-ph/0601068 |
| URL | https://arxiv.org/abs/quant-ph/0601068 |
| DOI | 10.1103/PhysRevA.72.062325 |
| Journal | PRA 72, 062325 (2005) |
Abstract
We have implemented an experimental set-up in order to demonstrate the feasibility of time-coding protocols for quantum key distribution. Alice produces coherent 20 ns faint pulses of light at 853 nm. They are sent to Bob with delay 0 ns (encoding bit 0) or 10 ns (encoding bit 1). Bob directs at random the received pulses to two different arms. In the first one, a 300 ps resolution Si photon-counter allows Bob to precisely measure the detection times of each photon in order to establish the key. Comparing them with the emission times of the pulses sent by Alice allows to evaluate the quantum bit error rate (QBER). The minimum obtained QBER is 1.62 %. The possible loss of coherence in the set-up can be exploited by Eve to eavesdrop the line. Therefore, the second arm of Bob set-up is a Mach-Zender interferometer with a 10 ns propagation delay between the two path. Contrast measurement of the output beams allows to measure the autocorrelation function of the received pulses that characterizes their average coherence. In the case of an ideal set-up, the value expected with the pulses sent by Alice is 0.576. The experimental value of the pulses autocorrelation function is found to be 0.541. Knowing the resulting loss of coherence and the measured QBER, one can evaluate the mutual information between Alice and Eve and the mutual information between Alice and Bob, in the case of intercept-resend attacks and in the case of attacks with intrication. With our values, Bob has an advantage on Eve of 0.43 bit per pulse. The maximum possible QBER corresponding to equal informations for Bob and Eve is 5.8 %. With the usual attenuation of fibres at 850 nm, it shows that secure key distribution is possible up to a distance of 2.75 km, which is sufficient for local links.
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"abstract": "We have implemented an experimental set-up in order to demonstrate the\nfeasibility of time-coding protocols for quantum key distribution. Alice\nproduces coherent 20 ns faint pulses of light at 853 nm. They are sent to Bob\nwith delay 0 ns (encoding bit 0) or 10 ns (encoding bit 1). Bob directs at\nrandom the received pulses to two different arms. In the first one, a 300 ps\nresolution Si photon-counter allows Bob to precisely measure the detection\ntimes of each photon in order to establish the key. Comparing them with the\nemission times of the pulses sent by Alice allows to evaluate the quantum bit\nerror rate (QBER). The minimum obtained QBER is 1.62 %. The possible loss of\ncoherence in the set-up can be exploited by Eve to eavesdrop the line.\nTherefore, the second arm of Bob set-up is a Mach-Zender interferometer with a\n10 ns propagation delay between the two path. Contrast measurement of the\noutput beams allows to measure the autocorrelation function of the received\npulses that characterizes their average coherence. In the case of an ideal\nset-up, the value expected with the pulses sent by Alice is 0.576. The\nexperimental value of the pulses autocorrelation function is found to be 0.541.\nKnowing the resulting loss of coherence and the measured QBER, one can evaluate\nthe mutual information between Alice and Eve and the mutual information between\nAlice and Bob, in the case of intercept-resend attacks and in the case of\nattacks with intrication. With our values, Bob has an advantage on Eve of 0.43\nbit per pulse. The maximum possible QBER corresponding to equal informations\nfor Bob and Eve is 5.8 %. With the usual attenuation of fibres at 850 nm, it\nshows that secure key distribution is possible up to a distance of 2.75 km,\nwhich is sufficient for local links.",
"arxiv_id": "quant-ph/0601068",
"authors": [
"William Boucher",
"Thierry Debuisschert"
],
"categories": [
"quant-ph"
],
"doi": "10.1103/PhysRevA.72.062325",
"journal_ref": "PRA 72, 062325 (2005)",
"title": "Experimental implementation of time-coding quantum key distribution",
"url": "https://arxiv.org/abs/quant-ph/0601068"
},
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