Condensed matter (CM) physics is perhaps most famous as the field that produced the transistor sixty years ago. Today, the behavior of electrons in various kinds of semiconductors remains an intensely active research area at JQI and elsewhere. CM deals with the properties of large aggregations of atoms or molecules, including their magnetic and electrical characteristics, and the ways in which the quantum properties of atoms influence those of their neighbors and of the material as a whole.

CM investigations are responsible for our knowledge of the "super" properties of matter in unusual states, such as superconductivity (absence of electrical resistance) and superfluidity (absence of viscosity or liquid friction), both of which are fundamentally quantum phenomena. Indeed, various arrangements of superconducting circuits can be employed to hold individual units of quantum information called quantum bits - or qubits for short - and JQI researchers are exploring those possibilities.

Another traditional CM subject involves the study and manipulation of atoms in various sorts of orderly geometrical arrangements. In a crystal, such as the silicon materials used to make microchips or the layered oxide arrays of superconductors, component atoms align themselves to form regular, repeating, three-dimensional patterns with consistent spacing. Even seemingly minor changes in the pattern can have huge effects on the material's chemical and electrical properties. But those changes and properties are hard to examine in bulk matter.

So JQI scientists employ a novel technique: They construct arrangements analogous to crystal structures by trapping super-cold atoms within geometric patterns formed by the intersection and interference of laser beams. These "artificial crystals" allow researchers to make carefully controlled changes in the pattern and observe the resulting properties. Theorists can test predictions and identify the most interesting configurations.

Another active area of JQI research involves the creation of macroscopic systems that can function as if they were individual quantum objects. This is possible because some quantum effects occur on relatively large spatial scales. One of them is the phenomenon known as "tunneling"-in which electrons can pass across an insulating barrier - as it occurs in superconducting loop structures called Josephson junctions. Although they are small by ordinary standards (on the order of a micron, or millionth of a meter), the junctions are about 10,000 times larger than an individual atom.

One or more of these devices can be arranged so that each one takes on the hallmark property of an atomic quantum qubit: superposition of states. Moreover, the states of different Josephson junctions, or "artificial atoms," can be entangled to provide the same sort of information-transfer and logic-gate potential found in atomic qubits. JQI researchers are testing various configurations of these junctions to find optimal designs and improve performance.