Abstract
We demonstrate for the first time the feasibility of free space quantum key distribution with continuous variables under real atmospheric conditions. More specifically, we transmit coherent polarization states over a 100 m free space channel on the roof of our institute's building. In our scheme, signal and local oscillator (LO) are combined in a single spatial mode, which auto-compensates atmospheric fluctuations and results in an excellent interference. Furthermore, the LO acts as a spatial and spectral filter, thus allowing unrestrained daylight operation.
Highlights
Quantum key distribution (QKD) [1, 2] is the process of establishing a secret shared key between two parties, traditionally named Alice and Bob
We demonstrate for the first time the feasibility of free space quantum key distribution with continuous variables under real atmospheric conditions
We focus on the first step, more precisely on the generation, transmission and measurement of coherent polarization states providing the raw data for QKD
Summary
Quantum key distribution (QKD) [1, 2] is the process of establishing a secret shared key between two parties, traditionally named Alice and Bob. The security is based on the laws of quantum mechanics, in contrast to classical schemes, where security relies on the unproven lack of efficient mathematical algorithms. Alice and Bob initially exchange quantum states over the quantum channel which might be completely under the control of an eavesdropper (called Eve). Alice and Bob use the classical channel to distil a secret key from measurement results taken during the first step. We focus on the first step, more precisely on the generation, transmission and measurement of coherent polarization states providing the raw data for QKD.
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