Quantum mechanics and effects were a subject of controversy when they were first proposed, a few decades ago. Now, most scientists agree with the theory, or at least acknowledge it to some extent. However, it's very difficult to prove that atoms exist in two states at the same time, seeing how one of the main demands of quantum physics holds that particles can behave in seemingly bizarre ways, as long as we don't observe them.

And, while scientists managed to measure atom traits like superposition (existing in two different states at the same time) and entanglement (the property of particles to influence each other regardless of the distance between them), they failed to do so with larger groups of atoms, or other constructs.

Now, experts at the California Institute of Technology (Caltech) have succeeded in devising a method of measuring such quantum effects in larger objects as well, made up of regular matter. The tool has the ability to accurately identify if either superposition or entanglement occurs, and to signal this aspect to researchers.

“Atoms and photons are intrinsically quantum mechanical, so it's no surprise if they behave in quantum mechanical ways. The question is, do these larger collections of atoms do this as well,” postdoctoral research scientist Matt LaHaye asks. He is working out of the lab of Caltech Professor of Physics, Applied Physics, and Bioengineering Michael L. Roukes, the co-director of the University Kavli Nanoscience Institute.

“It'd be weird to think of ordinary matter behaving in a quantum way, but there's no reason it shouldn't. If single particles are quantum mechanical, then collections of particles should also be quantum mechanical. And if that's not the case – if the quantum mechanical behavior breaks down – that means there's some kind of new physics going on that we don't understand,” Caltech Associate Professor of Applied Physics Keith Schwab, who has collaborated with Roukes and LaHaye for the new research, adds.

The scientists' new investigation technique consists of nothing more than a nanoelectromechanical system (NEMS) resonator, an incredibly small silicon-nitride beam, no more than two micrometers long, 0.2 micrometers wide, and weighing some 40 billionths of a milligram. The device has the amazing property of bending back and forth and resonating at high frequencies when a voltage is applied.

New to that NEMS resonator, experts built a qubit, the basic unit in quantum mechanics, a small speck of material between two insulating layers, in which pairs of electrons can travel. The qubit in this experiment only had the “ground” and “excited” phases built in, for the purpose of keeping the experiment as simple as possible.

“When the qubit is excited, the NEMS bridge vibrates at a higher frequency than it does when the qubit is in the ground state,” LaHaye explains. “Quantum jumps are, perhaps, the archetypal signature of behavior governed by quantum effects. To see these requires us to engineer a special kind of interaction between our measurement apparatus and the object being measured. Matt's results establish a practical and really intriguing way to make this happen,” Roukes concludes.