Efficient Editing of the CXCR4 Locus Using Cas9 Ribonucleoprotein Complexes Stabilized with Polyglutamic Acid.

Gene editing using the CRISPR/Cas9 system provides new opportunities to treat human diseases. Approaches aimed at increasing the efficiency of genome editing are therefore important to develop. To increase the level of editing of the CXCR4 locus, which is a target for gene therapy of HIV infection, the Cas9 protein was modified by introducing additional NLS signals and ribonucleoprotein complexes of Cas9 and guide RNA were stabilized with poly-L-glutamic acid. The approach allowed a 1.8-fold increase in the level of CXCR4 knockout in the CEM/R5 T cell line and a 2-fold increase in the level of knock-in of the HIV-1 fusion peptide inhibitor MT-C34 in primary CD4+ T lymphocytes.

Thermoelectric current in a graphene Cooper pair splitter.

Generation of electric voltage in a conductor by applying a temperature gradient is a fundamental phenomenon called the Seebeck effect. This effect and its inverse is widely exploited in diverse applications ranging from thermoelectric power generators to temperature sensing. Recently, a possibility of thermoelectricity arising from the interplay of the non-local Cooper pair splitting and the elastic co-tunneling in the hybrid normal metal-superconductor-normal metal structures was predicted. Here, we report the observation of the non-local Seebeck effect in a graphene-based Cooper pair splitting device comprising two quantum dots connected to an aluminum superconductor and present a theoretical description of this phenomenon. The observed non-local Seebeck effect offers an efficient tool for producing entangled electrons.

Noise of a superconducting magnetic flux sensor based on a proximity Josephson junction.

We demonstrate simultaneous measurements of DC transport properties and flux noise of a hybrid superconducting magnetometer based on the proximity effect (superconducting quantum interference proximity transistor, SQUIPT). The noise is probed by a cryogenic amplifier operating in the frequency range of a few MHz. In our non-optimized device, we achieve minimum flux noise ~4 µΦ0/Hz1/2, set by the shot noise of the probe tunnel junction. The flux noise performance can be improved by further optimization of the SQUIPT parameters, primarily minimization of the proximity junction length and cross section. Furthermore, the experiment demonstrates that the setup can be used to investigate shot noise in other nonlinear devices with high impedance. This technique opens the opportunity to measure sensitive magnetometers including SQUIPT devices with very low dissipation.

Lasing without inversion in circuit quantum electrodynamics.

We study the photon generation in a transmission line oscillator coupled to a driven qubit in the presence of a dissipative electromagnetic environment. It has been demonstrated previously that a population inversion in the qubit can lead to a lasing state of the oscillator. Here we show that the circuit can also exhibit the effect of "lasing without inversion." It arises since the coupling to the dissipative environment enhances photon emission as compared to absorption, similar to the recoil effect predicted for atomic systems. While the recoil effect is very weak, and so far elusive, the effect described here should be observable with realistic circuits. We analyze the requirements for system parameters and environment.

Magnetic field and contact resistance dependence of non-local charge imbalance.

Crossed Andreev reflection (CAR) in metallic nanostructures, a possible basis for solid-state electron entangler devices, is usually investigated by detecting non-local voltages in multi-terminal superconductor/normal metal devices. This task is difficult because other subgap processes may mask the effects of CAR. One of these processes is the generation of charge imbalance (CI) and the diffusion of non-equilibrium quasi-particles in the superconductor. Here we demonstrate a characteristic dependence of non-local CI on a magnetic field applied parallel to the superconducting wire, which can be understood by a generalization of the standard description of CI to non-local experiments. These results can be used to distinguish CAR and CI and to extract CI relaxation times in superconducting nanostructures. In addition, we investigate the dependence of non-local CI on the resistance of the injector and detector contacts and demonstrate a quantitative agreement with a recent theory using only material and junction characteristics extracted from separate direct measurements.

Relaxation and dephasing in a many-fermion generalization of the Caldeira-Leggett model.

We analyze a model system of fermions in a harmonic oscillator potential under the influence of a fluctuating force generated by a bath of harmonic oscillators. This represents an extension of the well-known Caldeira-Leggett model to the case of many fermions. Using the method of bosonization, we calculate Green's functions and discuss relaxation and dephasing of a single extra particle added above the Fermi sea. We also extend our analysis to a more generic coupling between system and bath that results in complete thermalization of the system.

Coulomb interaction and quantum transport through a coherent scatterer.

An interplay between charge discreteness, coherent scattering, and Coulomb interaction yields nontrivial effects in quantum transport. We derive a real-time effective action and an equivalent quantum Langevin equation for an arbitrary coherent scatterer and evaluate its current-voltage characteristics in the presence of interactions. Within our model, at large conductances G0 and low T (but outside the instanton-dominated regime), the interaction correction to G0 saturates and causes conductance suppression by a universal factor which depends only on the type of the conductor.