Emile Hoskinson

Quantum interference of superfluid 3He

Celebrated interference experiments have demonstrated the wave nature of light and electrons, quantum interference being the manifestation of wave–particle duality. More recently, double-path interference experiments have also demonstrated the quantum-wave nature of beams of neutrons, atoms and Bose–Einstein condensates. In condensed matter systems, double-path quantum interference is observed in the d.c. superconducting quantum interference device (d.c. SQUID). Here we report a double-path quantum interference experiment involving a liquid: superfluid 3He. Using a geometry analogous to the superconducting d.c. SQUID, we control a quantum phase shift by using the rotation of the Earth, and find the classic interference pattern with periodicity determined by the 3He quantum of circulation.

Oscillatory motion: Quantum whistling in superfluid helium-4

Fundamental considerations predict that macroscopic quantum systems such as superfluids and the electrons in superconductors will undergo oscillatory motion when forced through a small constriction. Here we induce these oscillations in superfluid helium-4 (4He) by pushing it through an array of nanometre-sized apertures. The oscillations, which are detected as an audible whistling sound, obey the so-called Josephson frequency relation and occur coherently among all the apertures. The discovery of this property in 4He at the relatively high temperature of 2 K (2,000 times higher than the temperature at which a related but different phenomenon occurs in 3He) may pave the way for a new class of practical rotation sensors of unprecedented precision.

Thermally Driven Josephson Oscillations in Superfluid ^4He

We find that a temperature differential can drive superfluid oscillations in 4He. The oscillations are excited by a heater which causes a time dependent temperature differential across an array of 70 nm apertures. By measuring the oscillation frequency and simultaneously determining both temperature and pressure differentials we prove the validity of the most general form of the Josephson frequency relation. These observations were made near saturated vapor pressure, within a few mK of the superfluid transition temperature.

Phase order and energy localization in acoustic propagation in random bubbly liquids

Abstract Propagation of acoustic waves in liquid media containing many air-filled bubbles is studied using a self-consistent approach. It is shown that under proper conditions, multiple scattering leads to a peculiar phase transition in acoustic propagation. When the phase transition occurs, not only the acoustic waves are confined in the neighborhood of the transmitting source, but a previously unsuspected collective behavior of the air bubbles appears, responsible for effective cancellation of the propagating wave. A novel phase diagram method is used to depict the phase transition.

Experimental demonstration of perturbative anticrossing mitigation using nonuniform driver Hamiltonians

Perturbative anticrossings have long been identified as a potential computational bottleneck for quantum annealing. This bottleneck can appear, for example, when a uniform transverse driver Hamiltonian is applied to each qubit. Previous theoretical research sought to alleviate such anticrossings by adjusting the transverse driver Hamiltonians on individual qubits according to a perturbative approximation. Here we apply this principle to a physical implementation of quantum annealing in a D-Wave 2000Q system. We use samples from the quantum annealing hardware and per-qubit anneal offsets to produce nonuniform driver Hamiltonians. On small instances with severe perturbative anticrossings, our algorithm yields an increase in minimum eigengaps, ground state success probabilities, and escape rates from metastable valleys. We also demonstrate that the same approach can mitigate biased sampling of degenerate ground states.

A Chemical Potential “Battery” for Superfluid 4He Weak Links

Research and development of superfluid weak links has been hindered by the absence of a source of dc chemical potential, similar to a simple battery or voltage source for analogous superconducting devices. We describe here a method for generating a dc chemical potential difference, Δμ across a weak link array in superfluid 4He. The presence of a Δμ forces quantum oscillations at a Josephson frequency, selectable by the adjustment of input power to a heater. We discuss a case in which the frequency locks onto a resonance feature where it exhibits remarkable stability, and amplitude magnification by a factor of 40.

Calibration Technique for Superfluid 4He Weak-Link Cells Based on the Fountain Effect

Studies of superfluid 4He weak‐links require calibration constants which permit the determination of the pressure and temperature differences which drive Josephson oscillations. We describe a technique for calibrating 4He weak‐link cells in which a heater is used to induce fountain pressures detected by the deflection of a diaphragm. The technique determines the diaphragm spring constant, the inner cell volume, and the thermal conductance of the inner cells walls. This information is used to convert the measured deflection of the diaphragm into the total chemical potential difference across the weak link.

Quantum whistling in superfluid helium-4: Oscillatory motion

Fundamental considerations predict that macroscopic quantum systems such as superfluids and the electrons in superconductors will undergo oscillatory motion when forced through a small constriction. Here we induce these oscillations in superfluid helium-4 (4He) by pushing it through an array of nanometre-sized apertures. The oscillations, which are detected as an audible whistling sound, obey the so-called Josephson frequency relation and occur coherently among all the apertures. The discovery of this property in 4He at the relatively high temperature of 2 K (2,000 times higher than the temperature at which a related but different phenomenon occurs in 3He) may pave the way for a new class of practical rotation sensors of unprecedented precision.

Development of a computer-based pulsed NMR thermometer

Abstract We have designed a fully computer-controlled pulsed NMR system, using the National Instruments PCI-6115 data acquisition board. We use it for millikelvin thermometry and have developed a special control program, written in LabVIEW, for this purpose. It can perform measurements of temperature via the susceptibility or the τ 1 dependence. This system requires little hardware, which makes it very versatile, easily reproducible and customizable.