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Semiconductor quantum dots (QDs) in planar germanium (Ge) heterostructures have emerged as front-runners for future hole-based quantum processors. Here, we present strong coupling between a hole charge qubit, defined in a double quantum dot (DQD) in planar Ge, and microwave photons in a high-impedance (Z r  = 1.3 kΩ) resonator based on an array of superconducting quantum interference devices (SQUIDs). Our investigation reveals vacuum-Rabi splittings with coupling strengths up to g 0 /2π = 260 MHz, and a cooperativity of C ~ 100, dependent on DQD tuning. Furthermore, utilizing the frequency tunability of our resonator, we explore the quenched energy splitting associated with strong Coulomb correlation effects in Ge QDs. The observed enhanced coherence of the strongly correlated excited state signals the presence of distinct symmetries within related spin functions, serving as a precursor to the strong coupling between photons and spin-charge hybrid qubits in planar Ge. This work paves the way towards coherent quantum connections between remote hole qubits in planar Ge, required to scale up hole-based quantum processors., Competing Interests: Competing interests: The authors declare no competing interests., (© 2024. The Author(s).)

Gate-tunable transmons (gatemons) employing semiconductor Josephson junctions have recently emerged as building blocks for hybrid quantum circuits. In this study, we present a gatemon fabricated in planar Germanium. We induce superconductivity in a two-dimensional hole gas by evaporating aluminum atop a thin spacer, which separates the superconductor from the Ge quantum well. The Josephson junction is then integrated into an Xmon circuit and capacitively coupled to a transmission line resonator. We showcase the qubit tunability in a broad frequency range with resonator and two-tone spectroscopy. Time-domain characterizations reveal energy relaxation and coherence times up to 75 ns. Our results, combined with the recent advances in the spin qubit field, pave the way towards novel hybrid and protected qubits in a group IV, CMOS-compatible material., (© 2024. The Author(s).)

In this work we theoretically investigate the possibility of observing strong coupling at mid-infrared frequencies within the group-IV semiconductor material platform. Our results show that the strong coupling condition is attainable in Ge/SiGe quantum wells integrated in hybrid metal-semiconductor microcavities, featuring a highly n-doped SiGe layer as one of the mirrors., Competing Interests: Conflict of interest: Authors state no conflicts of interest., (© 2024 the author(s), published by De Gruyter, Berlin/Boston.)

This study reports the experimental demonstration of the first waveguide-integrated SiGe modulator using a PIN diode operating in a wide spectral range of the mid-infrared region. At the wavelength of 10 µm, an extinction ratio up to 10 dB is obtained in injection regime and 3.2 dB in depletion regime. High speed operation is obtained, up to 1.5 GHz. Furthermore, the device can also operate as an integrated photodetector. Photodetection has thus been characterized from 5.2 µm to 10 µm wavelengths showing an internal responsivity around 1 mA/W, and a 3 dB electro-optical bandwidth of 32 MHz. These results show a significant advancement in integrated photodetectors and electro-optical modulators for mid-infrared spectroscopy., Competing Interests: Conflict of interest: Authors state no conflicts of interest., (© 2023 the author(s), published by De Gruyter, Berlin/Boston.)

Superconductor/semiconductor hybrid devices have attracted increasing interest in the past years. Superconducting electronics aims to complement semiconductor technology, while hybrid architectures are at the forefront of new ideas such as topological superconductivity and protected qubits. In this work, we engineer the induced superconductivity in two-dimensional germanium hole gas by varying the distance between the quantum well and the aluminum. We demonstrate a hard superconducting gap and realize an electrically and flux tunable superconducting diode using a superconducting quantum interference device (SQUID). This allows to tune the current phase relation (CPR), to a regime where single Cooper pair tunneling is suppressed, creating a [Formula: see text] CPR. Shapiro experiments complement this interpretation and the microwave drive allows to create a diode with ≈ 100% efficiency. The reported results open up the path towards integration of spin qubit devices, microwave resonators and (protected) superconducting qubits on  the same silicon technology compatible platform., (© 2024. The Author(s).)

A promising alternative to bulk materials for the nonlinear coupling of optical fields is provided by photonic integrated circuits based on heterostructures made of asymmetric-coupled quantum wells. These devices achieve a huge nonlinear susceptivity but are affected by strong absorption. Here, driven by the technological relevance of the SiGe material system, we focus on Second-Harmonic Generation in the mid-infrared spectral region, realized by means of Ge-rich waveguides hosting p-type Ge/SiGe asymmetric coupled quantum wells. We present a theoretical investigation of the generation efficiency in terms of phase mismatch effects and trade-off between nonlinear coupling and absorption. To maximize the SHG efficiency at feasible propagation distances, we also individuate the optimal density of quantum wells. Our results indicate that conversion efficiencies of ≈ 0.6%/W can be achieved in WGs featuring lengths of few hundreds µm only.

Introduction: Inpatient Addiction Consultation Services (ACS) fill an important need by connecting hospitalized patients with substance use disorders with resources for treatment; however, providers of these services may be at risk for burnout. In this qualitative study, we aimed to identify factors associated with burnout and, conversely, resilience among multidisciplinary providers working on ACS., Methods: We completed 26 semi-structured interviews with clinicians working on ACS, including physicians, social workers, and advanced practice providers. Twelve institutions across the country were represented. The study recruited participants via email solicitation to ACS directors and then via snowball sampling. We used an inductive, grounded theory approach to analyze data., Results: Providers described factors contributing to burnout and strategies for promoting resilience, and three main themes arose: (1) Systemic barriers contributed to provider burnout, (2) Engaging in meaningful work increased resilience, and (3) Team dynamics influenced perceptions of burnout and resilience., Conclusion: Our results suggest that hospital-based addiction medicine work is intrinsically rewarding for many providers and that engaging with other addiction providers to debrief challenging encounters or engage in advocacy work can be protective against burnout. However, administrative and systemic factors are frequent sources of frustration for providers of ACS. Structured debriefings may help to mitigate burnout. Furthermore, training to enhance providers' ability to engage effectively in advocacy work within and between hospital systems has the potential to promote resilience and protect against burnout among ACS providers., Competing Interests: Declaration of competing interest The authors have no conflicts of interest to disclose., (Copyright © 2022 Elsevier Inc. All rights reserved.)

In this work we theoretically investigate quantum confined Stark effect of intersubband transitions in asymmetric Ge/SiGe quantum wells for intensity modulation in the mid-infrared. Our calculations show that extinction ratios up to 1 dB and modulation speeds of several tens of GHz could be obtained in 100 µm long waveguides.