Calibration-Independent Certification of a Quantum Frequency Converter

Abstract

We report on a method to certify a unitary operation with the help of source and measurement apparatuses whose calibration throughout the certification process needs not be trusted. As in the device-independent paradigm our certification method relies on a Bell test, but it removes the need for high detection efficiencies by including the single additional assumption that non-detected events are independent of the measurement settings. The relevance of the proposed method is demonstrated experimentally with the certification of a quantum frequency converter. The experiment starts with the heralded creation of a maximally entangled two-qubit state between a single ${}^{40}$Ca${}^{+}$ ion and a 854nm photon. Entanglement preserving frequency conversion to the telecom band is then realized with a non-linear waveguide embedded in a Sagnac interferometer. The resulting ion-telecom photon entangled state is characterized by means of a Bell-CHSH test from which the quality of the frequency conversion is quantified. We demonstrate the successful frequency conversion with an average certified fidelity of $\ge 84\%$ and an efficiency $\ge 3.1\times 10^{-6}$ at a confidence level of $99\%$. This ensures the suitability of the converter for integration in quantum networks from a trustful characterization procedure.

References in corpus (19)

• A quantum network of clocks
• Self-testing of quantum systems: a review
• Distributed Quantum Computation Based-on Small Quantum Registers
• Multi-parameter estimation in networked quantum sensors
• Closing the detection loophole in Bell experiments using qudits
• Entangling single atoms over 33 km telecom fibre
• Analytic and nearly optimal self-testing bounds for the Clauser-Horne-Shimony-Holt and Mermin inequalities
• Long-distance distribution of atom-photon entanglement at telecom wavelength
• Light-matter entanglement over 50 km of optical fibre
• Polarization insensitive frequency conversion for an atom-photon entanglement distribution via a telecom network
• Verifying the quantumness of a channel with an untrusted device
• Certifying the building blocks of quantum computers from Bell's theorem
• Experimental investigation of partially entangled states for device-independent randomness generation and self-testing protocols
• Chained Bell Inequality Experiment with High-Efficiency Measurements
• Measurement Device Independent Verification of Quantum Channels
• Programmable atom-photon quantum interface
• Measurement-Device-Independent Verification of a Quantum Memory
• Experimental comparison of tomography and self-testing in certifying entanglement
• Simple Buehler-optimal confidence intervals on the average success probability of independent Bernoulli trials

Cited by in corpus (1)

• Verification of Continuous-Variable Quantum Memories