In experiments with superconducting quantum circuits, characterizing the photon statistics of propagating microwave fields is a fundamental task. We quantify the n^{2}+n photon number variance of ...thermal microwave photons emitted from a blackbody radiator for mean photon numbers, 0.05≲n≲1.5. We probe the fields using either correlation measurements or a transmon qubit coupled to a microwave resonator. Our experiments provide a precise quantitative characterization of weak microwave states and information on the noise emitted by a Josephson parametric amplifier.
Quantum communication protocols based on nonclassical correlations can be more efficient than known classical methods and offer intrinsic security over direct state transfer. In particular, remote ...state preparation aims at the creation of a desired and known quantum state at a remote location using classical communication and quantum entanglement. We present an experimental realization of deterministic continuous-variable remote state preparation in the microwave regime over a distance of 35 cm. By employing propagating two-mode squeezed microwave states and feedforward, we achieve the remote preparation of squeezed states with up to 1.6 dB of squeezing below the vacuum level. Finally, security of remote state preparation is investigated by using the concept of the one-time pad and measuring the von Neumann entropies. We find nearly identical values for the entropy of the remotely prepared state and the respective conditional entropy given the classically communicated information and, thus, demonstrate close-to-perfect security.
The bromodomain‐containing proteins BRD9 and BRD7 are part of the human SWI/SNF chromatin‐remodeling complexes BAF and PBAF. To date, no selective inhibitor for BRD7/9 has been reported despite its ...potential value as a biological tool or as a lead for future therapeutics. The quinolone‐fused lactam LP99 is now reported as the first potent and selective inhibitor of the BRD7 and BRD9 bromodomains. Development of LP99 from a fragment hit was expedited through balancing structure‐based inhibitor design and biophysical characterization against tractable chemical synthesis: Complexity‐building nitro‐Mannich/lactamization cascade processes allowed for early structure–activity relationship studies whereas an enantioselective organocatalytic nitro‐Mannich reaction enabled the synthesis of the lead scaffold in enantioenriched form and on scale. This epigenetic probe was shown to inhibit the association of BRD7 and BRD9 to acetylated histones in vitro and in cells. Moreover, LP99 was used to demonstrate that BRD7/9 plays a role in regulating pro‐inflammatory cytokine secretion.
BRD7 and BRD9 are bromodomain proteins and part of some chromatin‐remodeling complexes. A fragment lead was rapidly optimized through structure‐based design and exploitation of a stereoselective nitro‐Mannich/lactamization cascade process to give the first potent and selective BRD7/9 inhibitor, LP99. Treatment with LP99 led to displacement of BRD7 and BRD9 from chromatin and down‐regulation of the pro‐inflammatory cytokine IL‐6.
A combination of statistical studies and 18 case studies have been used to investigate the structure of the induced Martian magnetosphere. The different plasma and magnetic pressure forces on the ...dayside of the induced magnetosphere of Mars have been studied using 3.5 years of Mars Atmosphere and Volatile Evolution (MAVEN) and Mars Express (MEX) observations. We present estimates of typical values for the dominant pressure terms, that is, the thermal pressures of the ionosphere and the magnetosheath, the magnetic pressure of the magnetic pile‐up region, and the solar wind dynamic pressure. For 18 typical orbits the altitudes and relative distances of the pressure balance boundaries, the photoelectron boundary, the ion composition boundary, and the induced magnetosphere boundary are estimated. The magnetic pile‐up boundary is discussed but not further studied since earlier characterizations of the magnetic pile‐up boundary do not agree with our results. This study focuses on the transition region between the ionosphere and the magnetosheath on the dayside of Mars. We show that earlier definitions of the photoelectron boundary, ion composition boundary, and induced magnetosphere boundary do not characterize the transition region well, mainly because each boundary is based on measurements from only one or two instruments. In order to characterize the transition region correctly, changes in magnetic field strength and fluctuations, dominant ion species, electron and ion densities and energy distributions need to be considered. This article confirms a complex interaction between Mars and the solar wind and can explain why previous studies have had difficulties to describe the force balance.
Key Points
This article presents an overview of the Martian dayside magnetospheric structure based on the dominant pressure terms
Typical altitudes of the pressure balance boundaries, the PEB, ICB, and IMB are provided
We show that earlier defined boundaries are not a sufficient characterization of the ionosphere/magnetosheath transition region
In quantum illumination entangled light is employed to enhance the detection accuracy of an object when compared with the best classical protocol. On the other hand, cloaking is a stealth technology ...based on covering a target with a material deflecting the light around the object to avoid its detection. Here, we propose a quantum illumination protocol especially adapted to quantum microwave technology. This protocol seizes the phase-shift induced by some cloaking techniques, such as scattering reduction, allowing for a 3 dB improvement in the detection of a cloaked target. The method can also be employed for the detection of a phase-shift in bright environments in different frequency regimes. Finally, we study the minimal efficiency required by the photocounter for which the quantum illumination protocol still shows a gain with respect to the classical protocol.
The concept of parity describes the inversion symmetry of a system and is of fundamental relevance in the standard model, quantum information processing, and field theory. In quantum electrodynamics, ...parity is conserved and large field gradients are required to engineer the parity of the light-matter interaction operator. In this work, we engineer a potassiumlike artificial atom represented by a specifically designed superconducting flux qubit. We control the wave function parity of the artificial atom with an effective orbital momentum provided by a resonator. By irradiating the artificial atom with spatially shaped microwave fields, we select the interaction parity in situ. In this way, we observe dipole and quadrupole selection rules for single state transitions and induce transparency via longitudinal coupling. Our work advances the design of tunable artificial multilevel atoms to a new level, which is particularly promising with respect to quantum chemistry simulations with near-term superconducting circuits.
Two-mode squeezing is a fascinating example of quantum entanglement manifested in cross-correlations of non-commuting observables between two subsystems. At the same time, these subsystems themselves ...may contain no quantum signatures in their self-correlations. These properties make two-mode squeezed (TMS) states an ideal resource for applications in quantum communication. Here, we generate propagating microwave TMS states by a beam splitter distributing single mode squeezing emitted from distinct Josephson parametric amplifiers along two output paths. We experimentally study the fundamental dephasing process of quantum cross-correlations in continuous-variable propagating TMS microwave states and accurately describe it with a theory model. In this way, we gain the insight into finite-time entanglement limits and predict high fidelities for benchmark quantum communication protocols such as remote state preparation and quantum teleportation.
Abstract
The low-noise amplification of weak microwave signals is crucial for countless protocols in quantum information processing. Quantum mechanics sets an ultimate lower limit of half a photon to ...the added input noise for phase-preserving amplification of narrowband signals, also known as the standard quantum limit (SQL). This limit, which is equivalent to a maximum quantum efficiency of 0.5, can be overcome by employing nondegenerate parametric amplification of broadband signals. We show that, in principle, a maximum quantum efficiency of unity can be reached. Experimentally, we find a quantum efficiency of 0.69 ± 0.02, well beyond the SQL, by employing a flux-driven Josephson parametric amplifier and broadband thermal signals. We expect that our results allow for fundamental improvements in the detection of ultraweak microwave signals.
An implementation of carbon nanotube films in optoelectronic devices is still a challenging task which requires further improvement of their both optical and electrical properties. Here, we report an ...approach to enhance the transmittance of single-walled carbon nanotube films placed onto polymeric substrates without losses in the film conductivity by a low-power laser treatment. Laser pulses facilitate oxidation of nanotube caps thereby exposing iron catalytic particles due to fast local heating which leads to the oxidation of iron whereas the nanotube structure generally remains intact. Thus, we approached transmittance enhancement mainly across the visible range up to 4% (at 550 nm) associated with equivalent sheet resistance improvement of ca. 21%.
Display omitted
•Laser treatment is applied to carbon nanotube films placed over polymeric substrate to improve optoelectronic properties.•Carbon nanotube structure remains almost intact.•Low power laser irradiation facilitates 21%-gain of film equivalent sheet resistance.•Carbon nanotube film transmittance increases due to nanotube caps' and catalyst oxidation.
In a coupled system of one classical and one quantum mechanical degree of freedom, the quantum degree of freedom can facilitate the escape of the whole system. Such unusual escape characteristics ...have been theoretically predicted as the "Münchhausen effect." We implement such a system by shunting one of the two junctions of a dc SQUID with an additional capacitance. In our experiments, we detect a crossover between quantum and classical escape processes related to the direction of escape. We find that, under varying external magnetic flux, macroscopic quantum tunneling periodically alternates with thermally activated escape, a hallmark of the "Münchhausen effect."
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