Quantum Foundations
Loophole-free Bell tests, the measurement problem, contextuality, Wigner's-friend scenarios and experimental tests of collapse models.
Most influential
- Loophole-free Bell inequality violation using electron spins separated by 1.3 kilometres
For more than 80 years, the counterintuitive predictions of quantum theory have stimulated debate about the nature of reality. In his seminal work, John Bell proved that no theory of nature that obeys locality and realism can reproduce all the predictions of quantum theory. Bell showed that in any local realist theory the correlations between distant measure…
Article2,846 citationsarXiv:1508.05949doi:10.1038/nature15759 - Significant-Loophole-Free Test of Bell’s Theorem with Entangled Photons
Local realism is the worldview in which physical properties of objects exist independently of measurement and where physical influences cannot travel faster than the speed of light. Bell's theorem states that this worldview is incompatible with the predictions of quantum mechanics, as is expressed in Bell's inequalities. Previous experiments convincingly sup…
Article1,529 citationsarXiv:1511.03190doi:10.1103/physrevlett.115.250401 - Strong Loophole-Free Test of Local Realism
We present a loophole-free violation of local realism using entangled photon pairs. We ensure that all relevant events in our Bell test are spacelike separated by placing the parties far enough apart and by using fast random number generators and high-speed polarization measurements. A high-quality polarization-entangled source of photons, combined with high…
Article1,402 citationsarXiv:1511.03189doi:10.1103/physrevlett.115.250402 - Detection-Loophole-Free Test of Quantum Nonlocality, and Applications
We present a source of entangled photons that violates a Bell inequality free of the "fair-sampling" assumption, by over 7 standard deviations. This violation is the first experiment with photons to close the detection loophole, and we demonstrate enough "efficiency" overhead to eventually perform a fully loophole-free test of local realism. The entanglement…
Article477 citationsarXiv:1306.5772doi:10.1103/physrevlett.111.130406 - Loophole-free Bell inequality violation with superconducting circuits
Abstract Superposition, entanglement and non-locality constitute fundamental features of quantum physics. The fact that quantum physics does not follow the principle of local causality1–3 can be experimentally demonstrated in Bell tests4 performed on pairs of spatially separated, entangled quantum systems. Although Bell tests, which are widely regarded as a …
Abstract excerpt by Simon Storz et al., CC-BY, https://doi.org/10.1038/s41586-023-05885-0; truncated.
Article219 citationsdoi:10.1038/s41586-023-05885-0 - Practical device-independent quantum cryptography via entropy accumulation
Device-independent cryptography goes beyond conventional quantum cryptography by providing security that holds independently of the quality of the underlying physical devices. Device-independent protocols are based on the quantum phenomena of non-locality and the violation of Bell inequalities. This high level of security could so far only be established und…
Abstract excerpt by Rotem Arnon-Friedman et al., CC-BY, https://doi.org/10.1038/s41467-017-02307-4; truncated.
Article271 citationsdoi:10.1038/s41467-017-02307-4 - Device-independent quantum random-number generation
Randomness is critical for many information processing applications, including numerical modeling and cryptography. Device-independent quantum random number generation (DIQRNG) based on the loophole free violation of Bell inequality produces unpredictable genuine randomness without any device assumption and is therefore an ultimate goal in the field of quant…
Article258 citationsarXiv:1807.09611doi:10.1038/s41586-018-0559-3 - Loopholes in Bell inequality tests of local realism
Bell inequalities are intended to show that local realist theories cannot describe the world. A local realist theory is one where physical properties are defined prior to and independent of measurement, and no physical influence can propagate faster than the speed of light. Quantum-mechanical predictions for certain experiments violate the Bell inequality wh…
Article261 citationsarXiv:1407.0363doi:10.1088/1751-8113/47/42/424003 - Conclusive quantum steering with superconducting transition-edge sensors
Quantum steering allows two parties to verify shared entanglement even if one measurement device is untrusted. A conclusive demonstration of steering through the violation of a steering inequality is of considerable fundamental interest and opens up applications in quantum communication. To date all experimental tests with single photon states have relied on…
Article237 citationsarXiv:1111.0829doi:10.1038/ncomms1628 - Toward a Photonic Demonstration of Device-Independent Quantum Key Distribution
In this paper, we employ theoretical and experimental efforts and realize a proof-of-principle verification of device-independent QKD based on the photonic setup. On the theoretical side, we enhance the loss tolerance for real device imperfections by combining different approaches, namely, random post-selection, noisy preprocessing, and developed numerical m…
Article134 citationsarXiv:2110.01480doi:10.1103/physrevlett.129.050502 - Tomography of the quantum state of photons entangled in high dimensionsArticle162 citationsdoi:10.1103/physreva.84.062101
- High-Speed Device-Independent Quantum Random Number Generation without a Detection Loophole
Quantum mechanics provides means of generating genuine randomness that is impossible with deterministic classical processes. Remarkably, the unpredictability of randomness can be certified in a self-testing manner that is independent of implementation devices. Here, we present an experimental demonstration of self-testing quantum random number generation bas…
Article140 citationsarXiv:1709.06779doi:10.1103/physrevlett.120.010503 - Violation of a Temporal Bell Inequality for Single Spins in a Diamond Defect Center
Quantum non-locality has been experimentally investigated by testing different forms of Bell's inequality, yet a loophole-free realization has not been achieved up to now. Much less explored are temporal Bell inequalities, which are not subject to the locality assumption, but impose a constrain on the system's time-correlations. In this paper, we report on t…
Article145 citationsarXiv:1103.4949doi:10.1103/physrevlett.107.090401 - Generation of Fresh and Pure Random Numbers for Loophole-Free Bell Tests
We demonstrate extraction of randomness from spontaneous-emission events less than 36 ns in the past, giving output bits with excess predictability below $10^{-5}$ and strong metrological randomness assurances. This randomness generation strategy satisfies the stringent requirements for unpredictable basis choices in current "loophole-free Bell tests" of loc…
Article116 citationsarXiv:1506.02712doi:10.1103/physrevlett.115.250403 - Loophole-free Bell test using electron spins in diamond: second experiment and additional analysis
The recently reported violation of a Bell inequality using entangled electronic spins in diamonds (Hensen et al., Nature 526, 682-686) provided the first loophole-free evidence against local-realist theories of nature. Here we report on data from a second Bell experiment using the same experimental setup with minor modifications. We find a violation of the C…
Article95 citationsarXiv:1603.05705doi:10.1038/srep30289
Newest work
- Quantum field theory with scale-dependent weighted measures: nonlinear momentum representations, vacuum fluctuations, and causal structurePreprintarXiv:2610.39285
- Digital-Analog Quantum Neural Network with Long-Range InteractionsPreprintarXiv:2610.39847
- Process matrices on generalised theoriesPreprintarXiv:2610.40448
- On the gauge-invariant orbital angular momentum of vector optical vortices in the paraxial approximation and beyondPreprintarXiv:2610.40523
- Experimental Observation of Error-Resilience Phase Transition on Superconducting Quantum ProcessorPreprintarXiv:2610.38148
- Momentum-space entanglement and mutual information in Kaluza-Klein reductionPreprintarXiv:2610.37009
- Quantum Foundations Beyond Bell's Theorem: A Topical ReviewPreprintarXiv:2610.37854
- Electron-photon entanglement in real space from quantum electrodynamicsPreprintarXiv:2610.35467
- Network nonlocality with tripartite entangled sourcesPreprintarXiv:2610.35838
- Dynamical Tensor Train Approximation for Wigner--Fokker--Planck Equation with Applications to Open Quantum SystemsPreprintarXiv:2610.36257