# Research News

### Quantum speed up in an optical cavity

Control systems are ubiquitous, and as essential as they are easy to overlook. For instance, turning the dial on a thermostat feels as trivial as moving a piece on a board game, but this control system is actually quite complex.

### Qubit Chemistry

A big part of the burgeoning science of quantum computation is reliably storing and processing information in the form of quantum bits, or qubits. One of the obstacles to this goal is the difficulty of preserving the fragile quantum condition of qubits against unwanted outside influence even as the qubits interact among themselves in a programmatic way.

### Collecting Lost Light

Optical fibers are hair-like threads of glass used to guide light. Fibers of exceptional purity have proved an excellent way of sending information over long distances and are the foundation of modern telecommunication systems. Transmission relies on what’s called total internal reflection, wherein the light propagates by effectively bouncing back and forth off of the fiber’s internal surface.

### Moving out of equilibrium

Physicists use theoretical and experimental techniques to develop explanations of the goings-on in nature. Somewhat surprisingly, many phenomena such as electrical conduction can be explained through relatively simplified mathematical pictures — models that were constructed well before the advent of modern computation. And then there are things in nature that push even the limits of high performance computing and sophisticated experimental tools.

### Magic Wavelengths

Rydberg atoms, atoms whose outermost electrons are highly excited but not ionized, might be just the thing for processing quantum information. These outsized atoms can be sustained for a long time in a quantum superposition condition---a good thing for creating qubits---and they can interact strongly with other such atoms, making them useful for devising the kind of logic gates needed to process information. Scientists at JQI and at other labs are pursuing this promising research area.

### Tightening the Bounds on the Quantum Information 'Speed Limit'

If you’re designing a new computer, you want it to solve problems as fast as possible. Just how fast is possible is an open question when it comes to quantum computers, but JQI physicists have narrowed the theoretical limits for where that “speed limit” is. The work implies that quantum processors will work more slowly than some research has suggested.

### A quantum sensor for nanoscale electron transport

The word “defect” doesn’t usually have a good connotation--often indicating failure. But for physicists, one common defect known as a nitrogen-vacancy center (NV center) has applications in both quantum information processing and ultra-sensitive magnetometry, the measurement of exceedingly faint magnetic fields. In an experiment, recently published in *Science*, JQI Fellow Vladimir Manucharyan and colleagues at Harvard University used NV centers in diamond to sense the properties of magnetic field noise tens of nanometers away from the silver samples.

### Sharper Nanoscopy

A new study from Edo Waks' group has shown how to sharpen nanoscale microscopy (nanoscopy) even more by better locating the exact position of the light source. The improvement involves taking into account the phantom dipole induced in the surface of a nanowire by the presence of a nearby quantum dot. The interference of light emitted by the dot with light emitted (in effect) by the phantom distorts the estimation of the dot's true location.

### Modular Entanglement Using Atomic Ion Qubits

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