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A new paper published in The Physics of Natural Communications by Pedro R. Dieguez of the ABC Federal University in Brazil and an international team of scientists in the fields of quantum technology, functional quantum systems and quantum physics has developed a new framework of operational standards for physical reality. This attempt helps them understand quantum systems directly through the quantum state at each moment.
In the work, the team established a link between the output visibility and authenticity elements within the interferometer. The team provided proof of principle for the dual spin 1/2 system in an interferometry device within an NMR platform. These results confirm Bohr's original complementarity principle.
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In 1928, the Danish quantum physicist Bohr proposed the principle of complementarity. The principle of complementarity states that matter and radiation can be placed in a unified framework in which either element can behave as a wave or particle depending on the experimental setting. According to Bohr's natural philosophy, the nature of individuality in quantum systems is discussed relative to the definite setting of the experiment as a whole.
About a decade ago, physicists designed a quantum delay selection experiment (QDCE) that uses a beam splitter in a spatial quantum superposition to give the interferometer a "closed + open" configuration, a system that represents a hybrid "wave + particle" state.
The researchers previously coupled the target system to a quantum regulator and tested these ideas to show how photons exhibit wave- or particle-like behavior based on experimental techniques used to measure them. Based on the ability to smoothly interpolate statistics between wave-like and particle-like modes, physicists have proposed representations of changing behavior in the same system; claiming to have made a radical correction to Bohr's principle of complementarity.
Dieguez et al. re-evaluated QDCE (Quantum Delay Selection Experiment) through real-world elements in current experimental systems. To achieve this, they added a qubit as a particle-like state after passing through the first stacking device or beam splitter and phase shifter in the experimental setup to achieve the relative phase between the paths taken by the qubits. The team then activated the final stacking device to record the transition of the particle state to the wave state.
Based on the statistics of the circuit output, they deduced the propagation path of the qubits in the interferometer. To further understand this process, they calculated the authenticity in the circuit and discussed the elements of authenticity in the wave particle behavior in the quantum-controlled interference device. These results show how the state of the particle corresponds to the reality of the wave.
Thus, they noted in experimental methods that qubits always behave as a wave in an interferometer to demonstrate how physical realities are determined by quantum states at each moment.
Circuit schematic of a quantum-controlled interferometer. The blue box represents unitary operations, where it acts as a superposition device – a quantum network is equivalent to a spectrometer. Using the auxiliary qubits of the superposition state (quantum control system), the experiment realized the quantum-controlled unitary superposition device (red box). The original version of the quantum delay selection experiment, where the second beam splitter was prepared in a coherent superposition inside and outside the interferometer (configurations turned off and on, respectively). On the proposal of a real-world experiment with quantum control, the first beam splitter accepts quantum control. Although the measurements produce the same visibility in both experimental arrangements, the authenticity inside the interferometer is quite different.
Wave and particle authenticity as a function of visibility. (Quantum Delay Selection Experiment) The green diamond and dark red triangles are the RW (wave authenticity) and RP (particle authenticity) measured inside the interferometer, respectively. The blue square and red circle are the RW and RP measured inside the interferometer, respectively. The symbol represents the experimental result, and the dashed line is a numerical calculation of the pulse sequence simulating the initial experimental state. The data is parameterized by the visibility of the interferometer end. Estimation error by Monte Carlo propagation. The error of the data represented by a green diamond is less than the sign.
Probability pattern at the end of the interferometer (p0) as a function of the interferometer parameter (α) and the phase shifter (θ). (a) Delay selection scenario for quantum control. (b) The realist scenario for quantum control. (c) Visibility of an interferometer in a quantum control realism scenario (V). These symbols represent experimental results and numerical simulations (solid and dashed lines).
The team next proposed an experiment to solve problems in the previous experimental setup and effectively superimpose the wave and particle elements in reality. When the qubits entered the interferometer immediately after the phase shift, they calculated the state of the entire system. The interference device places the qubits in the superposition of paths to suggest the authenticity of the waves. When Dieguez et al. deactivate the controlled jamming device in the new QCRE setup, the qubits continue to move along their original path in the form of particles to show key differences from the original QDCE setup. In contrast to QDCE, physicists have noticed a strict equivalence relationship between the output statistics and the fluctuation behavior within the interferometer. These results confirm Bohr's original principle of complementarity.
Pulse sequence prepared in the initial state. The blue (orange) box represents x (y) local rotation by the angle indicated inside. These rotations are generated by transverse RF fields that resonate with 1H or 13C nuclei, with phase, amplitude, and duration being appropriately adjusted. A black dotted box with connections represents the free-time evolution of two spin scalar couplings. The box of the gray gradient indicates the magnetic field gradient, and the longitudinal direction is aligned with the symmetry axis of the spectrometer cylinder. All control parameters are optimized to create an initial pseudo-pure state with high fidelity (≿0.99).
The scientists then implemented these ideas in a proof-of-principle experiment that used a liquid nuclear magnetic resonance (NMR) device to encode two spin 1/2 qubits in a 13-C-labeled chloroform sample diluted with acetone-d6. They conducted experiments in a Varian 500 MHz spectrometer and used 13C nuclear spins to study the authenticity, wave, and particle characteristics of 1H nuclear spins, including interference paths. Of the four nuclear isotopes available, 1H, 13C, 35Cl, and 37Cl, the team only made adjustments to 1H and 13C. Using a combination of transverse RF pulses and resonances with each nucleus, the team performed an interferometry protocol with 1/2 quantum control of cell spin to observe interference patterns.
Pulse train of two interferometry schemes. (a) Sequence of the original version of the Quantum Delay Selection Experiment (QDCE). For optimization, the first overlay operation and the phase shifter are achieved by two rotations. Quantum-controlled interference is carried out using local operations on the system (1H) and controller (13C), as well as two free evolutions under scalar coupling; (b) a pulse sequence of the Quantum Control Reality Experiment (QCRE), in which quantum-controlled interference appears as the first operation, followed by phase shifters and interference operations. The most relevant contribution to the total duration of each experiment is free evolution, with two pulse sequences lasting approximately the same amount of time (≈14 ms).
In this way, Pedro R. Dieguez and colleagues used waves and particles to discuss the behavior of a quantum system through a dual-path device, generating some signals and statistics in the output. In the Quantum Delay Selection Experiment (QDCE), the scientists noticed that output visibility did not account for the specifics of the behavior of the qubits in the circuit. The team then introduced the Quantum Control Authenticity Experiment (QCRE) — a setup that could provide the original form of Bohr's principle of complementarity, unlike QDCE, where Dieguez et al. used QCRE to tune real-world wave particle elements, demonstrating the possibility of wave particle superposition in the setup to show "altered reality."
The study emphasizes the role of the principle of complementarity in altering the state of authenticity in quantum control systems, providing new insights into the nature of quantum causality, frames of reference, and the authenticity of wave and particle properties associated with quantum systems.
Reference Links:
https://phys.org/news/2022-04-physical-realism-experimentally-quantum-regulated-device.html