Modified superconductor synapse reveals exotic electron behavior
Electrons tend to avoid one another as they go about their business carrying current. But certain devices, cooled to near zero temperature, can coax these loner particles out of their shells. In extreme cases, electrons will interact in unusual ways, causing strange quantum entities to emerge. At the Joint Quantum Institute (JQI), Jimmy Williams’ group is working to develop new circuitry that could host such exotic states. These states have a feature that may make them useful in future quantum computers: They appear to be inherently protected from the destructive but unavoidable imperfections found in fabricated circuits. As described recently in Physical Review Letters, Williams’ team has reconfigured one workhorse superconductor circuit—a Josephson junction—to include a material suspected of hosting quantum states with boosted immunity.
Pristine quantum light source created at the edge of silicon chip
The smallest amount of light you can have is one photon, so dim that it’s pretty much invisible to humans. While imperceptible, these tiny blips of energy are useful for carrying quantum information around. Ideally, every quantum courier would be the same, but there isn’t a straightforward way to produce a stream of identical photons. This is particularly challenging when individual photons come from fabricated chips. Now, researchers at the Joint Quantum Institute (JQI) have demonstrated a new approach that enables different devices to repeatedly emit nearly identical single photons. The team, led by JQI Fellow Mohammad Hafezi, made a silicon chip that guides light around the device’s edge, where it is inherently protected against disruptions. Previously, Hafezi and colleagues showed that this design can reduce the likelihood of optical signal degradation. In a paper published online on Sept. 10 in Nature, the team explains that the same physics which protects the light along the chip’s edge also ensures reliable photon production.
Complexity test offers new perspective on small quantum computers
State-of-the-art quantum devices are not yet large enough to be called full-scale computers. The biggest comprise just a few dozen qubits—a meager count compared to the billions of bits in an ordinary computer’s memory. But steady progress means that these machines now routinely string together 10 or 20 qubits and may soon hold sway over 100 or more. In the meantime, researchers are busy dreaming up uses for small quantum computers and mapping out the landscape of problems they’ll be suited to solving. A paper by researchers from the Joint Quantum Institute (JQI) and the Joint Center for Quantum Information and Computer Science (QuICS), published recently in Physical Review Letters, argues that a novel non-quantum perspective may help sketch the boundaries of this landscape and potentially even reveal new physics in future experiments.