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Spectral characterization of noise environments that lead to the decoherence of qubits is critical to developing robust quantum technologies. While dynamical decoupling offers one of the most successful approaches to characterize noise spectra, it necessitates applying large sequences ofπpulses that increase the complexity and cost of the method. Here, we introduce a noise spectroscopy method that utilizes only the Fourier transform of free induction decay or spin echo measurements, thus removing the need for the application manyπpulses. We show that our method faithfully recovers the correct noise spectra for a variety of different environments (including 1/f-type noise) and outperforms previous dynamical decoupling schemes while significantly reducing their experimental overhead. We also discuss the experimental feasibility of our proposal and demonstrate its robustness in the presence of statistical measurement error. Our method is applicable to a wide range of quantum platforms and provides a simpler path toward a more accurate spectral characterization of quantum devices, thus offering possibilities for tailored decoherence mitigation.

Physics laboratory courses (PLC) have been recently the topic of several research studies examining their effectiveness at reaching their goals. As a result, a discussion about the effectiveness of traditional PLC for students’ content knowledge, skills, and “expert-thinking” acquisition has developed. Critical for the investigation of students learning in those settings has been the development of research-based assessments tools. An example of those is the Colorado Learning Attitudes about Science Survey for Experimental Physics (E-CLASS). Recently, we translated the E-CLASS into German and set up a centralized survey administration system for instructors, allowing data acquisition and automated data analysis. Previously, we described this process and presented the preliminary results of the study of the introductory PLC at the University of Potsdam (UP). Here, we present an extended study that allows us to make stronger conclusions about students’ views about experimental physics at the UP. Overall, we find that students at US institutions have a higher level of “expert-like” views than students at the UP.

mCherry is one of the most successfully applied monomeric red fluorescent proteins (RFPs) for in vivo and in vitro imaging. However, questions pertaining to the photostability of the RFPs remain and rational further engineering of their photostability requires information about the fluorescence quenching mechanism in solution. To this end, NMR spectroscopic investigations might be helpful, and we present the near-complete backbone NMR chemical shift assignment to aid in this pursuit.

We present a simple and effective method to create highly entangled spin states on a faster timescale than that of the commonly employed one-axis twisting (OAT) model. We demonstrate that by periodically driving the Dicke Hamiltonian at a resonance frequency, the system effectively becomes a two-axis countertwisting Hamiltonian, which is known to quickly create Heisenberg limit scaled entangled states. For these states we show that simple quadrature measurements can saturate the ultimate precision limit for parameter estimation determined by the quantum Cramér-Rao bound. An example experimental realization of the periodically driven scheme is discussed with the potential to quickly generate momentum entanglement in a recently described experimental vertical cavity system. We analyze effects of collective dissipation in this vertical cavity system and find that our squeezing protocol can be more robust than the previous realization of OAT.

Methods to probe and understand the dynamic response of materials following impulsive excitation are important for many fields, from materials and energy sciences to chemical and neuroscience. To design more efficient nano, energy, and quantum devices, new methods are needed to uncover the dominant excitations and reaction pathways. In this work, we implement a newly-developed superlet transform—a super-resolution time-frequency analytical method—to analyze and extract phonon dynamics in a laser-excited two-dimensional (2D) quantum material. This quasi-2D system, 1T-TaSe₂, supports both equilibrium and metastable light-induced charge density wave (CDW) phases mediated by strongly coupled phonons. We compare the effectiveness of the superlet transform to standard time-frequency techniques. We find that the superlet transform is superior in both time and frequency resolution, and use it to observe and validate novel physics. In particular, we show fluence-dependent changes in the coupled dynamics of three phonon modes that are similar in frequency, including the CDW amplitude mode, that clearly demonstrate a change in the dominant charge-phonon couplings. More interestingly, the frequencies of the three phonon modes, including the strongly-coupled CDW amplitude mode, remain time- and fluence-independent, which is unusual compared to previously investigated materials. Our study opens a new avenue for capturing the coherent evolution and couplings of strongly-coupled materials and quantum systems.

Ultracold collisions of the polyatomic species CaOH are considered, in internal states where the collisions should be dominated by long-range dipole–dipole interactions. The computed rate constants suggest that evaporative cooling can be quite efficient for these species, provided they start at temperatures achievable by laser cooling. The rate constants are shown to become more favorable for evaporative cooling as the electric field increases. Moreover, long-range dimer states (CaOH)${}_2^{*}$are predicated to occur, having lifetimes on the order of microseconds.

Communication networks have multiple users, each sending and receiving messages. A multiple access channel (MAC) models multiple senders transmitting to a single receiver, such as the uplink from many mobile phones to a single base station. The optimal performance of a MAC is quantified by a capacity region of simultaneously achievable communication rates. We study the two-sender classical MAC, the simplest and best-understood network, and find a surprising richness in both a classical and quantum context. First, we find that quantum entanglement shared between senders can substantially boost the capacity of a classical MAC. Second, we find that optimal performance of a MAC with bounded-size inputs may require unbounded amounts of entanglement. Third, determining whether a perfect communication rate is achievable using finite-dimensional entanglement is undecidable. Finally, we show that evaluating the capacity region of a two-sender classical MAC is in fact NP-hard.

Protocols for designing and manipulating qubits with ultracold alkali atoms in 3D optical lattices are introduced. These qubits are formed from two‐atom spin superposition states that create a decoherence‐free subspace immune to stray magnetic fields, dramatically improving coherence times while still enjoying the single‐site addressability and Feshbach resonance control of state‐of‐the‐art alkali atom systems. The protocol requires no continuous driving or spin‐dependent potentials, and instead relies upon the population of a higher motional band to realize naturally tunable in‐site exchange and cross‐site superexchange interactions. As a proof‐of‐principle example of their utility for entanglement generation for quantum computation, it is shown that the cross‐site superexchange interactions can be used to engineer 1D cluster states. Explicit protocols for experimental preparation and manipulation of the qubits are also discussed, as well as methods for measuring more complex quantities such as out‐of‐time‐ordered correlation functions (OTOCs).