Modulator autocalibration methods for quantum key distribution
US7720228B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Feb 24, 2005 |
| Grant date | May 18, 2010 |
| Priority date | — |
| Expiry date | Oct 12, 2027 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04B10/70
- WIPO fieldTelecommunications
- WIPO sectorElectrical engineering
Abstract
Methods for calibrating the modulators in a QKD system (100) are disclosed. The methods include setting the voltage (VB) of Bob's modulator (MB) to a positive value and then adjusting the voltage (VA) of Alice's modulator (MA) in both the positive and negative direction to obtain overall relative phase modulations that result in maximum and minimum photon counts (N) in the two single-photon detectors (32a, 32b). Bob's modulator voltage is then set to a negative value and the process repeated. When the basis voltages (VB(1), VB(2), VA(1), VA(2), VA(3) and VA(4)) are established, the QKD system is operated with intentionally selected incorrect bases at Bob and Alice to assess orthogonality of the basis voltages by assessing whether or not the probability of photon detection at the detectors is 50:50. If not, the modulator voltages are adjusted to be orthogonal. This involves changing Bob's basis voltage (VB(1) and/or VB(2)) and repeating the process until a 50:50 detector count distribution is obtained. The calibration method can be carried out periodically during QKD system operation to ensure optimum or near-optimum operation of the modulators.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.