A Two-Photon Experiment Concerning Delayed Choice and Hidden Variables in Quantum Mechanics

Juergen Baldzuhn, Ernst Mohler, W. Martienssen

He-Liang Huang, Yi-Han Luo, B. Bai +14 more

Wheeler's delayed-choice experiment investigates the indeterminacy of wave-particle duality and the role played by the measurement apparatus in quantum theory. Due to the inconsistency with classical physics, it has been generally believed that it is not possible to reproduce the delayed-choice experiment using a hidden-variable theory. Recently, it was shown that Wheeler's delayed-choice experiment can be explained by a causal two-dimensional hidden-variable theory [R. Chaves, G. B. Lemos, and J. Pienaar, Phys. Rev. Lett. 120, 190401 (2018)]. Here, we carry out a delayed-choice experiment by using photon states that are spacelike separated and demonstrate that the experiment is consistent with quantum theory but inconsistent with any causal two-dimensional hidden-variable theory in a device-independent manner. This demonstrates that causality can be used to test quantum theory in a complementary way to the Bell and Leggett-Garg tests.

Tao Xin, Hang Li, Bi-Xue Wang +1 more

The puzzling properties of quantum mechanics, i.e., wave-particle duality, entanglement, and superposition, have been dissected experimentally over the past decades. However, hidden-variable (HV) models based on three classical assumptions of wave-particle objectivity, determinism, and independence strive to explain the same experiments or even defeat quantum mechanics. Meanwhile, the steady development of quantum technologies continues to enable us to test experimentally the predictions of quantum mechanics and HV theories. We report an experimental demonstration of an entanglement-assisted quantum delayed-choice scheme using a liquid nuclear magnetic resonance quantum-information processor. This experiment is based on the recently proposed scheme [R. Ionicioiu et al., Nat. Commun. 5. 3997 (2014)], which predicted different results for quantum mechanics and HV theories. In our experiments, the intensities and the visibilities of the interference are consistent with the theoretical predictions of quantum mechanics. The results show that a contradiction with the experiments is indeed appearing when all three assumptions of the HV models are combined, though any two of those assumptions are compatible with the experiments.

C. O. Alley, O. Jakubowicz, C. A. Steggerda +1 more

Pranav D. Chandarana, Angela A. Baiju, Sumit Mukherjee +3 more

Wave-particle duality of quantum objects is one of the most striking features of quantum physics and has been widely studied in past decades. Developments of quantum technologies enable us to experimentally realize several quantum phenomena. Observation of wave-particle morphing behavior in the context of the quantum delayed-choice experiment (QDCE) is one of them. Adopting the scheme of QDCE, we demonstrate how the coexistence of wave and particle nature emerges as a consequence of the uncertainty in the quantum controlled experimental setup, using a five-qubit cloud-based quantum processor. We also show that an entanglement-assisted scheme of the same reproduces the predictions of quantum mechanics. We put evidence that a local hidden variable theory is incompatible with quantum mechanical predictions by comparing the variation of intensities obtained from our experiment with hidden variable predictions.

S. Malin