大质量物体也可达到量子态

Researchers have created a "quantum state" in the largest object yet.

研究人员已使用大质量物体创造出“量子状态”。

The "quantum resonator" can be seen with the naked eye

Such states, in which an object is effectively in two places at once, have until now only been accomplished（完成，实现） with single particles, atoms and molecules.

In this experiment, published in the journal Nature, scientists produced a quantum state in an object billions of times larger than previous tests.

The team says the result could have significant implications（启示） in quantum（量子） computing.

One of the pillars of quantum mechanics is the idea that objects absorb and emit energy in tiny discrete（离散的，不连续的） packets known as quanta.

This is akin to（相同，类似） a piece of coloured glass, which can absorb a certain colour of light. That light is made up of photons - light particles - and the glass atoms absorb only photons with the quanta (or amount) of energy that corresponds to that colour.

At the atomic level, quantum mechanics predicts - and experiments demonstrate - a number of surprising effects.

If all the energy that an atom gets from the jostling（冲撞） atoms in its environment is removed by cooling it to phenomenally low temperatures, it can reach its "quantum ground state" - no more energy can be removed.

If just one quantum of energy is then carefully put back in, the atom can be said to be in two states at the same time.

Although only one quantum of energy is put in, any measurements will show either one or two quanta.

Strictly, the atom has both and is said to be in a superposition（叠加，重合） of states.

Down to ground

These superpositions of states have long been predicted to be useful for a pursuit known as quantum computing; if used in place of the zeroes and ones of digital computing, a quantum computer would be vastly more powerful.

However, creating these states in anything bigger than single atoms and molecules has proven difficult, because the larger an object is, the more tricky it becomes to isolate it from its environment and put it in its ground state.

"There is this question of where the dividing line is between the quantum world and the classical world we know," said Andrew Cleland of the University of California, Santa Barbara.

"We know perfectly well that things are not in two places at the same time in our everyday experience, but this fundamental theory of physics says that they can be," he told BBC News.

Now, Professor Cleland and his team have moved that dividing line, using an object just big enough to be seen with the naked eye.

They used a tiny piece of what is known as a piezoelectric material（压电材料） , which expands and contracts when an electrical current is run through it.

A current applied at a certain frequency causes it to expand and contract regularly and, just like a violin（小提琴） string, the material has a frequency at which it is inclined to vibrate.

They connected this resonator（共鸣器，共振器） to an electric circuit that the team has been developing for three years. This can be tuned to put in just one quantum of electrical energy.

They cooled the whole apparatus（装置，设备） down to a thousandth of a degree above absolute zero and confirmed that their resonator was in its quantum ground state.

The researchers designed the system so that they could "pump in" just one quantum of electrical energy at a time and see the oscillator（振荡器） begin to vibrate as it converted that quantum into one quantum of vibrational energy.

As it vibrated, the team showed that the resonator was in one of the slippery（滑的，不稳定的） superpositions（叠加，重合） of states, with both one and zero quanta of energy.