We propose a quantum imaging-inspired setup for measuring gravitational fields using an atom that emits a photon at one of two possible locations. The atom acquires a gravitationally induced quantum phase that it shares with the photon. By restoring the path identity of the atom after its interaction with the gravitational field, the gravitationally induced phase can be measured using photon interferometry without the need for additional measurements on the atom. Through repeated measurements with varying interferometric setups, the gravitational potential and inertial acceleration can be deduced.

We investigate the Maximum Cut (MaxCut) problem on different graph classes with the quantum approximate optimization algorithm (QAOA) using symmetries. In particular, heuristics on the relationship between graph symmetries and the approximation ratio achieved by a QAOA simulation are considered. To do so, we first solve the MaxCut problem on well-known graphs, then we consider simple and controllable perturbations of the graph and find again the approximate MaxCut with the QAOA. Through an analysis of the spectrum of the graphs and their perturbations, as well as a careful study of the associated automorphism groups, we aim to extract valuable insight into how symmetry impacts the performance of QAOA. These insights can then be leveraged to heuristically reduce the quantum circuit complexity, the number of training steps, or the number of parameters involved, thus enhancing the efficiency and effectiveness of QAOA-based solutions.

Radical pairs in the flavoprotein cryptochrome are central to various magnetically sensitive biological processes, including the proposed mechanism of avian magnetoreception. Cryptochrome's molecular chirality has been hypothesized to enhance magnetic field effects via the chirality-induced spin selectivity (CISS) effect, yet the mechanism underlying this enhancement remains unresolved. In this work, we systematically investigate the impact of CISS on the directional magnetic sensitivity of prototypical radical pair reactions, analyzing two distinct models—one generating spin polarization and, for the first time, one generating coherence. We find that CISS-induced spin polarization significantly enhances magnetic sensitivity by introducing triplet character into the initial state and reinforcing the quantum Zeno effect, aligning with enhancements observed in triplet-born radical pairs subject to strongly asymmetric recombination. In contrast, CISS-generated spin coherence does not provide a significant improvement in sensitivity. These findings indicate that CISS is not itself a universal enhancer of sensitivity or coherence in radical pair reactions, and its influence must be evaluated case by case, particularly in relation to the quantum Zeno effect. Additionally, we provide a unified interpolation scheme for modeling CISS-influenced initial states and recombination dynamics, encompassing the principal models currently discussed in the literature for singlet and triplet precursors.

The description of how different quantum features, such as non-Markovianity and quantumness, interact in quantum channels is an important step in designing and managing quantum systems. Here, we look at three non-Markovian dephasing channels: pink, brown, and static noise. We investigate and evaluate various measures of non-Markovianity in these channels. Indeed, the proposed measurements include trace norm, entropy, and quantum capacity. We investigate the effect of non-Markovianity on the quantum nature of these channels. Our results show that increasing the degree of non-Markovianity in the suggested channels does not always improve the channel's quantumness. Furthermore, given the aforementioned quantum channels, the l2 norm of quantum coherence and mixedness satisfies the trade-off relation, which is critical for understanding how quantum resources and noise interact in open quantum systems.

We report the experimental observation of transient dynamics in the weak probe coherence under electromagnetically induced transparency (EIT) in hot Rb atoms with a buffer gas. By modulating the control beam in a non-adiabatic fashion, we have examined the corresponding changes in probe transparency. Upon switching the control beam on, the system evolves through multiple dynamical processes before reaching steady-state transparency. We have decoded each of those dynamical processes region by region and notably observed two-photon damped Rabi oscillations, Raman gain, and direct dark state rotation during this evolution. For the theoretical insight, we have numerically solved the time-dependent density matrix elements for a Λ system, incorporating the buffer gas effects phenomenologically into these equations. Our findings provide a detailed understanding of transient and steady-state dynamics in EIT systems, highlighting the interplay between coherent and incoherent processes and the role of the buffer gas in modulating the evolution. The buffer medium extended relevant timescales, thus enhancing the coherence and stability of the atomic system, which are key factors for practical implementations in precision metrology and quantum optics.

We demonstrate the imaging of localized surface electric (E) field effects on the atomic spectrum in a vapor cell used in Rydberg atom-based sensors. These surface E-fields can result from an induced electric charge distribution on the surface. Induced surface charge distributions can dramatically perturb the atomic spectrum, hence degrading the ability to perform electrometry. These effects become pronounced near the walls of the vapor cell, posing challenges for vapor cell miniaturization. Using a fluorescence imaging technique, we investigate the effects of surface charge on the atomic spectrum generated with electromagnetically induced transparency (EIT). Our results reveal that visible light (480 and 511 nm), i.e., the coupling laser used in two-photon Rydberg EIT schemes, generates localized patches of charge or dipoles where this light interacts with the glass walls of the vapor cell, while a three-photon Rydberg EIT scheme using only near-infrared wavelength lasers shows no measurable field induction. Additionally, imaging in a vacuum chamber where a glass plate is placed between large electrodes confirms that the induced charge is positive. We further validate these findings by studying the photoelectric effect with broadband light during EIT and impedance measurements. These results demonstrate the power of the fluorescence imaging technique to study localized E-field distributions in vapor cells and to target the photoelectric effect of the alkali-exposed glass of vapor cells as a major disruptor in Rydberg atom-based sensors.

In order to leverage quantum computers for machine learning tasks such as image classification, consideration is required. Noisy Intermediate-Scale Quantum (NISQ) computers have limitations that include noise, scalability, read-in and read-out times, and gate operation times. Therefore, strategies should be devised to mitigate the impact complex datasets that can have on the overall efficiency of a quantum machine learning pipeline. This may otherwise lead to excessive resource demands or noise. We apply a classical feature extraction using a ResNet10-inspired convolutional autoencoder to reduce dataset dimensionality and extract abstract, meaningful features before feeding them into a quantum layer. The chosen quantum layer is a quantum-enhanced support vector machine (QSVM), as SVMs typically do not require large sample sizes to identify patterns in data and have short-depth quantum circuits, which limits the impact of noise. The autoencoder is trained to extract meaningful features through image reconstruction, aiming to minimize the mean squared error across a training set of images. We use three datasets to illustrate the pipeline: HTRU-1, MNIST, and CIFAR-10. We include a quantum-enhanced one-class support vector machine (QOCSVM) for the highly unbalanced HTRU-1 set, with classical machine learning results for comparison. HTRU-2 is also included to serve as a benchmark for a dataset with meaningful features. The autoencoder achieved near-perfect reconstruction and high accuracy for MNIST, while CIFAR-10 showed poorer performance due to image complexity, and HTRU-1 struggled due to the imbalance in the dataset. The varying performance across datasets highlights the need to balance dimensionality reduction and prediction performance using quantum methods.

Non-Abelian Thouless pumping intertwines adiabatic quantum control and topological quantum transport, and it holds potential for quantum metrology and computing. In this work, we introduce a ladder model featuring two doubly degenerate bands and we show that adiabatic manipulation of the lattice parameters results in non-Abelian Thouless pumping, inducing both the displacement of an initially localized state and a geometric unitary transformation within the degenerate subspace. Additionally, we show that the structure and symmetry of the ladder model can be understood through its connection to a Yang monopole model. The proposed Hamiltonian can be realized using cold atoms in optical lattices, enabling the experimental demonstration of non-Abelian Thouless pumping in a genuinely quantum many-body system.

The native oxide layer formed on aluminum (Al) surfaces in superconducting quantum circuits is a significant source of two-level system defects, which couple with electric fields and degrade quantum coherence. Recent research has explored etching, encapsulation, and other surface treatments as potential strategies to mitigate the formation of oxides at air interfaces in these circuits. This study demonstrates a novel approach to passivate the Al–air interface using a molecular self-assembled monolayer (SAM). Freshly prepared Al thin films were passivated with SAMs by immersing the Al-coated silicon substrates in SAM solutions. X-ray photoelectron spectroscopy (XPS) confirms the successful binding of the SAM and the absence of further aluminum oxide growth. Moreover, the passivation remains stable after aging for 15 days in ambient conditions, as evidenced by XPS and contact angle measurements. Scanning electron microscopy analyses further support the binding of the SAM to the Al surface and mitigation of oxide growth. These findings suggest that SAM-based passivation offers a promising method for reducing microwave loss and improving the performance of Al-based superconducting quantum circuits.

Semiconductor quantum dots (QDs), being an auspicious outcome of nanotechnology, have wide technological applications based on their simple synthetic procedures, tunable photoluminescent properties, and effective optical stability. However, their utilization in sensing, imaging, and optoelectronic applications is limited due to their intrinsic drawback of fluorescence intermittency, which not only hinders precise biological imaging due to challenges in tracking individual target molecules but also gives inaccurate measurements and creates complications in data analysis due to long dark (off) states that remain on the time scale of milliseconds to minutes. In order to resolve this problem, research work is being carried out on a large scale to elucidate the mechanism following blinking and approaches to suppress it. This review explicitly highlights the key mechanisms: A type (Auger), B type, near band edge carrier (C type), and D type, responsible for the blinking effect in QDs, and explores the effective methods for its suppression including shell engineering, halide vacancy filling, and passivating the surface with ligands, polymers, noble metals, and plasmonic as well as N-Type semiconductor substrates to enhance their efficiency on practical grounds. Nearly non-blinking QDs with an on-state for 99% of the time have been synthesized by shell engineering. The suppression of blinking leads to improved performance and enhanced efficiency of QD-based devices. According to the literature reports, these methodologies efficiently suppress the blinking phenomenon, even approaching near unity (≈1) photoluminescence quantum yield, which is notable. Finally, the current review discusses the advantages of blinking suppression specifically in biomedical applications such as single particle tracking, in vivo and in vitro imaging, and biosensing.