Friday Roundup: Quantum Measurement Without Disruption, and Humans are Spontaneously Generous

Scientists recently measured a quantum state without changing it, and researchers discover that human beings appear to be generous when they think intuitively, and greedy when they think carefully and deliberately.

A Quantum State is Measured Without Being Destroyed

A refrigeration device at the Quantum Nanoelectronics Laboratory, Berkley, where the experiment was conducted

The Heisenberg uncertainty principle describes how the act of measuring a tiny system changes your ability to make predictions about the future of the system. A recent experiment at the University of California, however, proved that this doesn’t necessarily mean what you think it does.

A bit more background first. In many ways, elementary “particles” (like electrons and protons) aren’t really particles at all. They move more like waves, meaning they can spread out, interfere with themselves, and be in more than one place at the same time.

The only reason we call them “particles” is because certain properties are measured in discrete units. A wave of electrons can carry an arbitrary amount of energy, but it can only carry properties like mass and charge in a certain number of units. In other words, a wave of electrons could carry a mass of 1 or 2 electrons, but not 1.5.

Since it’s impossible to absorb 1.5 electrons, this means that an electron can only get absorbed in one place, even though it travels like a wave. This is the primary reason why we still call them “particles.”

Think of quantum measurement like this. Pass a beam of light through a magnifying glass. The more you focus the beam of light at one point, the more it will blur out later on. Single particles blur out this same way, so that it becomes difficult to know where the particle will get absorbed.

What we can know is the exact probability the particle will get absorbed at a specific place, as long as nothing interferes with it. This is a bit like saying you know exactly what the blur of light on the wall will look like.

Some press outlets have (very incorrectly) implied that this new experiment allowed the researchers to violate this arrangement, miraculously measuring a particle’s position without changing it’s future state. This would be like refocusing the beam of light without changing the shape or size of the blur on the wall. As far as we know, it’s impossible.

What they actually did was measure it’s quantum state without changing it.

This probably sounds like the same thing, so let me elaborate.

Going back to to the magnifying glass analogy, measuring the quantum state would be like measuring the distribution of the whole beam of light, without focusing it. In other words, its position is still spread out, and you haven’t changed how spread out the beam will be when it hits the wall. What you have done is figured out exactly how blurred out the beam of light will be when it hits the wall.

The reason this is so important is because quantum systems are very delicate and easily interfered. Future computer systems may be able to harness a system’s quantum state to perform powerful calculations, but only if we can prevent this interference. What this experiment proved is that it is possible to detect this interference, and even correct it, without collapsing the system.

The actual experiment dealt with quantum oscillators in a superconductor, but the essential principles are the same.

Related: Quantum: Einstein, Bohr, and the Great Debate about the Nature of Reality

Humans are Generous When Spontaneous but Greedy When Calculating

David Rand (center) Joshua Greene (left) Martin Nowak (right), authors of the paper

Researchers at Harvard and Cambridge wanted to investigate how cooperative and competitive decisions were made. In particular, they wanted to know if cooperation was done intuitively, or if it was the result of an act of restraint. The results are bad news for cynics.

In ten “games” designed to simulate economic decisions, they discovered that those who came to a decision faster were more cooperative.

Of course, that wasn’t enough to claim causality, so they deliberately forced them to think fast in some cases or to think slowly and carefully in others. What they found was that when they were forced to make decisions quickly, they erred on the side of being “giving.” When forced to think slowly and deliberately, they became less cooperative and willing to share.

Another “induction” technique primed the participants to think with their instincts. This also resulted in more generous behavior.

While this is by no means a comprehensive study, it certainly suggests that human beings, by their nature, are a cooperative species. Cooperation likely played an important part in our evolutionary origins.

It’s worth noting that “intuition” is not necessarily the same thing as “instinct,” however. The experimenters instead concluded that “cooperative heuristics are developed in daily life where cooperation is typically advantageous.”

Related: The Evolution of Cooperation: Revised Edition

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