| 1. |
- Gonzales-Ureta, Junior R., et al.
(författare)
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Device-independent quantum key distribution based on Bell inequalities with more than two inputs and two outputs
- 2021
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Ingår i: Physical Review A: covering atomic, molecular, and optical physics and quantum information. - 2469-9926 .- 2469-9934. ; 103:5
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Tidskriftsartikel (refereegranskat)abstract
- Device-independent quantum key distribution (DI-QKD) offers the strongest form of security against eavesdroppers bounded by the laws of quantum mechanics. However, a practical implementation is still pending due to the requirement of combinations of visibility and detection efficiency that are beyond those possible with current technology. This mismatch motivates the search for DI-QKD protocols that can close the gap between theoretical and practical security. In this work, we present two DI-QKD protocols whose security relies on Bell inequalities with more than two inputs and two outputs. We show that, for maximally entangled states and perfect visibility, a protocol based on a Bell inequality with three inputs and four outputs requires a slightly lower detection efficiency than the protocols based on Bell inequalities with two inputs and two outputs.
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| 2. |
- Mironowicz, Piotr, et al.
(författare)
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Quantum randomness protected against detection loophole attacks
- 2021
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Ingår i: Quantum Information Processing. - : SPRINGER. - 1570-0755 .- 1573-1332. ; 20:1
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Tidskriftsartikel (refereegranskat)abstract
- Device and semi-device-independent private quantum randomness generators are crucial for applications requiring private randomness. However, they are vulnerable to detection inefficiency attacks and this limits severely their usage for practical purposes. Here, we present a method for protecting semi-device-independent private quantum randomness generators in prepare-and-measure scenarios against detection inefficiency attacks. The key idea is the introduction of a blocking device that adds failures in the communication between the preparation and measurement devices. We prove that, for any detection efficiency, there is a blocking rate that provides protection against these attacks. We experimentally demonstrate the generation of private randomness using weak coherent states and standard avalanche photo-detectors.
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| 3. |
- Pokorny, Fabian, et al.
(författare)
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Tracking the Dynamics of an Ideal Quantum Measurement
- 2020
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 124:8
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Tidskriftsartikel (refereegranskat)abstract
- The existence of ideal quantum measurements is one of the fundamental predictions of quantum mechanics. In theory, an ideal measurement projects a quantum state onto the eigenbasis of the measurement observable, while preserving coherences between eigenstates that have the same eigenvalue. The question arises whether there are processes in nature that correspond to such ideal quantum measurements and how such processes are dynamically implemented in nature. Here we address this question and present experimental results monitoring the dynamics of a naturally occurring measurement process: the coupling of a trapped ion qutrit to the photon environment. By taking tomographic snapshots during the detection process, we show that the process develops in agreement with the model of an ideal quantum measurement with an average fidelity of 94%.
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| 4. |
- Smania, Massimiliano, et al.
(författare)
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Experimental certification of an informationally complete quantum measurement in a device-independent protocol
- 2020
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Ingår i: Optica. - 2334-2536. ; 7:2, s. 123-128
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Tidskriftsartikel (refereegranskat)abstract
- Minimal informationally complete positive operator-valued measures (MIC-POVMs) are special kinds of measurement in quantum theory in which the statistics of their d(2)-outcomes are enough to reconstruct any d-dimensional quantum state. For this reason, MIC-POVMs are referred to as standard measurements for quantum information. Here, we report an experiment with entangled photon pairs that certifies, for what we believe is the first time, a MIC-POVM for qubits following a device-independent protocol (i.e., modeling the state preparation and the measurement devices as black boxes, and using only the statistics of the inputs and outputs). Our certification is achieved under the assumption of freedom of choice, no communication, and fair sampling.
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