Fig. 2: Schematic of our proposed SPIR system. | Light: Science & Applications

Fig. 2: Schematic of our proposed SPIR system.

From: Experimental symmetric private information retrieval with measurement-device-independent quantum network

Fig. 2

a The SPIR system comprises two layers, the QKD layer and the application layer, which operate independently except for the transfer of secret keys. In the QKD layer, quantum transmitters are paired for key distribution, which includes procedures of quantum state preparation, quantum state measurement, and classical post-processing. In the application layer, each party obtains and manages the generated secret keys for the implementation of the SPIR protocol. The black dashed arrows represent the direction of the classical communication, while the orange solid lines represent quantum channels for QKD. b Schematic of the MDI QKD implementation. LD laser diode, IM intensity modulator, PM phase modulator, BS beam splitter, AMZI asymmetric Mach–Zehnder interferometer, ATT optical attenuator, PL optical power limiter, OS Optical switch, PC polarisation controller, PBS polarising beam splitter, SNSPD superconducting nanowire single-photon detector

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