In this paper, we present an all-optical method to produce shell-shaped traps for ultracold atoms in microgravity. Our scheme exploits optical double dressing of the ground state to create a short range strongly repulsive central potential barrier. Combined with a long range attractive central potential, this barrier forms the shell trap. We demonstrate that a pure spherical bubble, reaching the quasi-2D regime for standard atom numbers, could be formed from two crossed beams with a parabolic profile. An analytical study shows that the relevant characteristics of the trap depend on the ratio of the ground and excited state polarizabilities and the lifetime of the excited state. As a benchmark, we provide quantitative analysis of a realistic configuration for rubidium ensembles, leading to a 250 Hz transverse confinement for a 35 μm radius bubble and a trap residual scattering rate of less than 10 s−1.

What defines the operational boundary between quantum information and classical magnetism? We present a model-independent methodology for detecting characteristic scales in quantum systems through generalized susceptibility analysis χ(σ)=|d〈O〉/dσ|, where σ represents observation scales across spatial, temporal, and decoherence dimensions. Through comprehensive experiments on a Rigetti Ankaa-3 quantum processor, we identify an operational threshold at γc=0.6737±0.036 under tested noise profiles, exhibiting exceptional peak clarity κ=8.58—the sharpest signal observed across all phenomena. This pronounced transition, validated through bootstrap analysis and multiple susceptibility metrics, suggests critical-like behavior in the quantum-to-classical crossover, though we carefully refrain from claiming a thermodynamic phase transition. The framework successfully extracts characteristic scales without prior theoretical knowledge: correlation length ξ=8.00 qubits, distinct ordering timescales for ferromagnetic (tc=0.36) versus antiferromagnetic (tc=0.91) systems, and the quantum critical field hc=1.821 in the transverse-field Ising model. Robustness analysis confirms stability across smoothing parameters, methods, and metric definitions. Beyond providing actionable guidance for noisy intermediate-scale quantum-era quantum computing, our findings suggest that magnetic correlations exhibit characteristic transitions at specific decoherence scales—an operational perspective connecting quantum information theory and condensed matter physics. While framing this as methodological advance rather than fundamental physics, the identification of critical-like information-to-physics transitions provides practical diagnostics for quantum device characterization and optimization.

Atomic sensors using light–matter interactions, in particular, atomic clocks and atom interferometers, have the potential to complement optical gravitational-wave detectors in the mid-frequency regime. Although both rely on interference, the interfering components of clocks are spatially colocated, whereas atom interferometers are based on spatial superpositions. Both the electromagnetic fields that drive the transitions and generate superpositions, while propagating through spacetime, as well as the atoms themselves as massive particles are influenced by gravitational waves, leading to effective potentials that induce phase differences inferred by the sensor. In this work, we analyze the effects of these potentials on atomic clocks and atom interferometers in the laboratory frame. We show that spatial superpositions in atom interferometers, both light-pulse and guided ones, give rise to a gravitational-wave signal. Although these spatial superpositions are suppressed for clocks, we show that the light pulses driving internal transitions measure the spatial distance between the centers of two separate clocks. We highlight that this mechanism only yields a sensitivity if both clocks, including possible trapping setups, move on geodesics given by the gravitational wave. While such configurations are natural for satellite free-fliers, terrestrial optical clocks usually rely on stationary traps, rendering them insensitive to leading order. Moreover, we show that both sensors can be enhanced by composite interrogation protocols in a common framework. To this end, we propose a pulse sequence that can be used for large-momentum-transfer atom interferometers and for hyper-echo atomic clocks, leading to signal enhancement and noise suppression.

This study presents a comprehensive design approach focusing on quantum chip signal amplification by Josephson parametric amplifiers, and an integrated receiver for detecting ultra-low-level quantum signals. Quantum theory is used to analyze the dynamics of a transmon qubit coupled to a transmission line, entanglement between them, and design a parametric amplifier to amplify the quantum signals. Integration of these quantum devices with a 45 nm CMOS system-on-chip receiver creates a sophisticated blend of quantum and classical elements. The transmon qubit and parametric amplifier as a quantum chip, operating at 10 mK, are evaluated for key quantum metrics such as entanglement, Stoke projector probabilities, and parametric amplifier gain. Simultaneously, the resulting receiver combines high-performance components, including a low-noise amplifier with 0.76 dB noise figure in a broad bandwidth, a sweepable 5.0 GHz sinusoidal wave generator, and a purpose-designed mixer for C-band to zero-intermediate frequency (IF) conversion. An intermediate frequency amplifier with flat 26 dB gain and its low-pass filter property generates a pure sinusoidal wave at zero-IF, suitable for subsequent processing at room temperature. This design achieves a notable balance with low power consumption (∼122 mW), a noise figure less than 0.9 dB, high gain (∼65 dB), a wide bandwidth of 3.6 GHz, and compact dimensions (0.6 × 0.4 mm2). The fully integrated receiver, capable of reading out at least 90 qubits, positions this design for potential applications in quantum computing. Post-simulation validations at room temperature underscore the promising and innovative nature of this approach.

Decoherence is a manifestation of the coupling of a system with its environment. The resulting loss of information can hamper the functioning of quantum devices; hence, there is a need to understand its origin and dynamics. Decoherence can stem from entanglement, but it can also be classical in nature. Indeed, methods have been developed to understand whether qubit-environment entanglement (QEE) is actually present in some important classes of quantum channels—pure dephasing. Their practicality resides in the fact that they only require accessing the system qubit. In this paper, we show an implementation of this technique in a photonic quantum channel simulator via a scheme that has been tailored to the system under study. By controlling the input state of the environment in our simulation, we can check the occurrence of qubit environment entanglement in simple, yet insightful test cases. Our results showcase the usefulness and experimental relevance of the QEE witnessing technique.

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.

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.

Collective modes are coherent excitations in Bose–Einstein condensates (BECs), and their study provides insight into the macroscopic quantum phenomena that govern these systems. Collective mode frequencies can be used to probe the properties of BECs, such as the trap geometry, the interatomic interactions, and the presence of defects; hence, it is essential to develop methods for high-resolution determination of collective mode frequencies. A standard technique consists of a single pulse of an external oscillatory field, which the authors denote Rabi-like due to the analogy with the field of nuclear magnetic resonances. In this work, the authors propose a method to achieve a better resolution than the Rabi-like protocol, which consists of two oscillating fields separated in time, which the authors call Ramsey-like. The authors focus on BECs in harmonic traps, considering mainly the quadrupole and breathing modes for different trap anisotropy values and comparing the results using single and double excitation periods. First, the authors employ a variational approach with a Thomas–Fermi ansatz, which gives rise to dynamical equations that are numerically solved. Then, the authors modeled the problem as a three-level system, offering a concise and alternative description of the same dynamics, enabling the idea of coherent control of these collective modes. Both approaches show that the Ramsey-like protocol provides a better resolution than the Rabi-like. This offers the possibility of measuring collective mode frequencies with higher precision, which is important in experiments where they are used as indirect measurements of properties that are difficult to probe.

Non-symmorphic chiral crystals hosting higher-fold fermions and bosons are of great interest due to the recent experimental realizations. The specialty of these higher-fold fermions and bosons is that they possess long Fermi arcs connecting the Brillouin zone boundaries. In this work, using first-principles calculations, we examine the higher-fold topological phases in the phonon spectrum and electronic band structure of ternary chiral crystals BaXY (X = Pt, Pd; Y = P, As, Sb, Bi). Our detailed analysis reveals the symmetry-protected spin-1 Weyl and charge-2 Dirac topological phonon phase in the phonon spectrum. Contrastingly, the electronic states exhibit intriguing fourfold and sixfold fermionic states under spin–orbit coupling. Interestingly, we found the emergence of giant topological surface Fermi arcs in both phonon and electronic phases. Our findings highlight the coexistence of higher-fold topological phases in both the electronic and phononic states in all of the studied ternary chiral crystals, which may serve future topological device applications.

The nitrogen-vacancy (NV) center in diamond is an increasingly popular quantum sensor for microscopy of electrical current, magnetization, and spins. However, efficient NV–sample integration with a robust, high-quality interface remains an outstanding challenge to realize scalable, high-throughput microscopy. In this work, we characterize a diamond micro-chip (DMC) containing a (111)-oriented NV ensemble and demonstrate its utility for high-resolution quantum microscopy. We perform strain imaging of the DMC and find minimal detrimental strain variation across a field of view of tens of micrometer. We find good ensemble NV spin coherence and optical properties in the DMC, suitable for sensitive magnetometry. We then use the DMC to demonstrate wide-field microscopy of electrical current and show that diffraction-limited quantum microscopy can be achieved. We also demonstrate the deterministic transfer of DMCs with multiple materials of interest for next-generation electronics and spintronics. Lastly, we develop a polymer-based technique for DMC placement. This work establishes the DMC's potential to expand the application of NV quantum microscopy in materials, device, geological, biomedical, and chemical sciences.