@article{20976, abstract = {We present an experimental demonstration of an impedance-engineered Josephson parametric amplifier (IEJPA) fabricated in a single-step lithography process. Impedance-engineering is implemented using a lumped-element series LC circuit. We use a simpler lithography process where the entire device—impedance transformer and Josephson parametric amplifier (JPA)—is patterned in a single electron beam lithography step, followed by a double-angle Dolan-bridge technique for Al–AlOx–Al deposition. We observe amplification with 18 dB gain over a wide 400 MHz bandwidth centered around 5.3 GHz with added noise approaching the quantum limit, and a saturation power of −114 dBm. To accurately explain our experimental results, we extend existing theories for IEJPAs to incorporate the full sine nonlinearity of both the JPA and the transformer. Our work provides a route to simpler realization of broadband JPAs and a theoretical foundation for a regime of JPA operation that has been less explored in literature.}, author = {Patel, Lipi and Hawaldar, Samarth and Panikkar, Aditya and Shankar, Athreya and Suri, Baladitya}, issn = {1077-3118}, journal = {Applied Physics Letters}, number = {25}, publisher = {AIP Publishing}, title = {{Impedance-engineered Josephson parametric amplifier with single-step lithography}}, doi = {10.1063/5.0290636}, volume = {127}, year = {2025}, } @article{14342, abstract = {We propose a simple method to measure nonlinear Kerr refractive index in mid-infrared frequency range that avoids using sophisticated infrared detectors. Our approach is based on using a near-infrared probe beam which interacts with a mid-IR beam via wavelength-non-degenerate cross-phase modulation (XPM). By carefully measuring XPM-induced spectral modifications in the probe beam and comparing the experimental data with simulation results, we extract the value for the non-degenerate Kerr index. Finally, in order to obtain the value of degenerate mid-IR Kerr index, we use the well-established two-band formalism of Sheik-Bahae et al., which is shown to become particularly simple in the limit of low frequencies. The proposed technique is complementary to the conventional techniques, such as z-scan, and has the advantage of not requiring any mid-infrared detectors.}, author = {Lorenc, Dusan and Alpichshev, Zhanybek}, issn = {0003-6951}, journal = {Applied Physics Letters}, number = {9}, publisher = {AIP Publishing}, title = {{Mid-infrared Kerr index evaluation via cross-phase modulation with a near-infrared probe beam}}, doi = {10.1063/5.0161713}, volume = {123}, year = {2023}, } @article{11417, abstract = {Over the past few years, the field of quantum information science has seen tremendous progress toward realizing large-scale quantum computers. With demonstrations of quantum computers outperforming classical computers for a select range of problems,1–3 we have finally entered the noisy, intermediate-scale quantum (NISQ) computing era. While the quantum computers of today are technological marvels, they are not yet error corrected, and it is unclear whether any system will scale beyond a few hundred logical qubits without significant changes to architecture and control schemes. Today's quantum systems are analogous to the ENIAC (Electronic Numerical Integrator And Computer) and EDVAC (Electronic Discrete Variable Automatic Computer) systems of the 1940s, which ran on vacuum tubes. These machines were built on a solid, nominally scalable architecture and when they were developed, nobody could have predicted the development of the transistor and the impact of the resulting semiconductor industry. Simply put, the computers of today are nothing like the early computers of the 1940s. We believe that the qubits of future fault-tolerant quantum systems will look quite different from the qubits of the NISQ machines in operation today. This Special Topic issue is devoted to new and emerging quantum systems with a focus on enabling technologies that can eventually lead to the quantum analog to the transistor. We have solicited both research4–18 and perspective articles19–21 to discuss new and emerging qubit systems with a focus on novel materials, encodings, and architectures. We are proud to present a collection that touches on a wide range of technologies including superconductors,7–13,21 semiconductors,15–17,19 and individual atomic qubits.18 }, author = {Sigillito, Anthony J. and Covey, Jacob P. and Fink, Johannes M and Petersson, Karl and Preble, Stefan}, issn = {0003-6951}, journal = {Applied Physics Letters}, number = {19}, publisher = {American Institute of Physics}, title = {{Emerging qubit systems: Guest editorial}}, doi = {10.1063/5.0097339}, volume = {120}, year = {2022}, } @article{9331, abstract = {Quantum entanglement has been generated and verified in cold-atom experiments and used to make atom-interferometric measurements below the shot-noise limit. However, current state-of-the-art cold-atom devices exploit separable (i.e., unentangled) atomic states. This perspective piece asks the question: can entanglement usefully improve cold-atom sensors, in the sense that it gives new sensing capabilities unachievable with current state-of-the-art devices? We briefly review the state-of-the-art in precision cold-atom sensing, focusing on clocks and inertial sensors, identifying the potential benefits entanglement could bring to these devices, and the challenges that need to be overcome to realize these benefits. We survey demonstrated methods of generating metrologically useful entanglement in cold-atom systems, note their relative strengths and weaknesses, and assess their prospects for near-to-medium term quantum-enhanced cold-atom sensing.}, author = {Szigeti, Stuart S. and Hosten, Onur and Haine, Simon A.}, issn = {0003-6951}, journal = {Applied Physics Letters}, number = {14}, publisher = {AIP Publishing}, title = {{Improving cold-atom sensors with quantum entanglement: Prospects and challenges}}, doi = {10.1063/5.0050235}, volume = {118}, year = {2021}, } @article{21552, abstract = {We present full-Maxwell topology-optimization design of a single-piece multilayer metalens, about 10 wavelengths λ in thickness, which simultaneously focuses over a 60° angular range and a 23% spectral bandwidth without suffering chromatic or angular aberration, a “plan-achromat.” At all angles and frequencies, it achieves diffraction-limited focusing (Strehl ratio >0.8) and an absolute focusing efficiency of >50%. Both 2D and 3D axisymmetric designs are presented, optimized over ∼105 degrees of freedom. We also demonstrate shortening the lens-to-sensor distance while producing the same image as for a longer “virtual” focal length and maintaining plan-achromaticity. These proof-of-concept designs demonstrate the ultra-compact multifunctionality that can be achieved by exploiting the full wave physics of subwavelength designs and motivate future work on design and fabrication of multilayer metaoptics.}, author = {Lin, Zin and Roques-Carmes, Charles and Christiansen, Rasmus E. and Soljačić, Marin and Johnson, Steven G.}, issn = {1077-3118}, journal = {Applied Physics Letters}, number = {4}, publisher = {AIP Publishing}, title = {{Computational inverse design for ultra-compact single-piece metalenses free of chromatic and angular aberration}}, doi = {10.1063/5.0035419}, volume = {118}, year = {2021}, } @article{8746, abstract = {Research in the field of colloidal semiconductor nanocrystals (NCs) has progressed tremendously, mostly because of their exceptional optoelectronic properties. Core@shell NCs, in which one or more inorganic layers overcoat individual NCs, recently received significant attention due to their remarkable optical characteristics. Reduced Auger recombination, suppressed blinking, and enhanced carrier multiplication are among the merits of core@shell NCs. Despite their importance in device development, the influence of the shell and the surface modification of the core@shell NC assemblies on the charge carrier transport remains a pertinent research objective. Type-II PbTe@PbS core@shell NCs, in which exclusive electron transport was demonstrated, still exhibit instability of their electron ransport. Here, we demonstrate the enhancement of electron transport and stability in PbTe@PbS core@shell NC assemblies using iodide as a surface passivating ligand. The combination of the PbS shelling and the use of the iodide ligand contributes to the addition of one mobile electron for each core@shell NC. Furthermore, both electron mobility and on/off current modulation ratio values of the core@shell NC field-effect transistor are steady with the usage of iodide. Excellent stability in these exclusively electron-transporting core@shell NCs paves the way for their utilization in electronic devices. }, author = {Miranti, Retno and Septianto, Ricky Dwi and Ibáñez, Maria and Kovalenko, Maksym V. and Matsushita, Nobuhiro and Iwasa, Yoshihiro and Bisri, Satria Zulkarnaen}, issn = {1077-3118}, journal = {Applied Physics Letters}, number = {17}, publisher = {AIP Publishing}, title = {{Electron transport in iodide-capped core@shell PbTe@PbS colloidal nanocrystal solids}}, doi = {10.1063/5.0025965}, volume = {117}, year = {2020}, } @article{796, abstract = {We present the fabrication and characterization of an aluminum transmon qubit on a silicon-on-insulator substrate. Key to the qubit fabrication is the use of an anhydrous hydrofluoric vapor process which selectively removes the lossy silicon oxide buried underneath the silicon device layer. For a 5.6 GHz qubit measured dispersively by a 7.1 GHz resonator, we find T1 = 3.5 μs and T∗2 = 2.2 μs. This process in principle permits the co-fabrication of silicon photonic and mechanical elements, providing a route towards chip-scale integration of electro-opto-mechanical transducers for quantum networking of superconducting microwave quantum circuits. The additional processing steps are compatible with established fabrication techniques for aluminum transmon qubits on silicon.}, author = {Keller, Andrew J and Dieterle, Paul and Fang, Michael and Berger, Brett and Fink, Johannes M and Painter, Oskar}, issn = {0003-6951}, journal = {Applied Physics Letters}, number = {4}, publisher = {American Institute of Physics}, title = {{Al transmon qubits on silicon on insulator for quantum device integration}}, doi = {10.1063/1.4994661}, volume = {111}, year = {2017}, }