Demonstration of Tunable Three-Body Interactions between Superconducting Qubits.

Nonpairwise multiqubit interactions present a useful resource for quantum information processors. Their implementation would facilitate more efficient quantum simulations of molecules and combinatorial optimization problems, and they could simplify error suppression and error correction schemes. Here, we present a superconducting circuit architecture in which a coupling module mediates two-local and three-local interactions between three flux qubits by design. The system Hamiltonian is estimated via multiqubit pulse sequences that implement Ramsey-type interferometry between all neighboring excitation manifolds in the system. The three-local interaction is coherently tunable over several MHz via the coupler flux biases and can be turned off, which is important for applications in quantum annealing, analog quantum simulation, and gate-model quantum computation.

Suppressing relaxation in superconducting qubits by quasiparticle pumping.

Dynamical error suppression techniques are commonly used to improve coherence in quantum systems. They reduce dephasing errors by applying control pulses designed to reverse erroneous coherent evolution driven by environmental noise. However, such methods cannot correct for irreversible processes such as energy relaxation. We investigate a complementary, stochastic approach to reducing errors: Instead of deterministically reversing the unwanted qubit evolution, we use control pulses to shape the noise environment dynamically. In the context of superconducting qubits, we implement a pumping sequence to reduce the number of unpaired electrons (quasiparticles) in close proximity to the device. A 70% reduction in the quasiparticle density results in a threefold enhancement in qubit relaxation times and a comparable reduction in coherence variability.

Hepatic clearance and drug metabolism using isolated perfused rat liver.

The isolated perfused rat liver (IPRL) has been extensively used as an intact organ model for determination of hepatic clearance and metabolism of drugs. The IPRL model can also be applied to determine physiologically based pharmacokinetics. Since the IPRL model avoids neural and hormonal interferences and excludes influences from absorption processes and non-hepatic elimination routes such as renal excretion and respiration, it provides a relatively clean hepatic system to study metabolism and pharmacokinetics. It is especially useful to model the hepatic uptake associated with plasma protein binding and transport. The viability of the liver can be evaluated based on the gross appearance, bile flow, perfusion pressure, lactate dehydrogenase release, and oxygen uptake. The protocol describes the surgical procedures for isolation of the rat liver, a hemoglobin-free perfusion method, and application of this model for determination of hepatic uptake and clearance.