快猫短视频

I ALMOST didn鈥檛 write this column because I worried that it might give people the wrong impression about quantum mechanics. So let me start by saying that I wholeheartedly believe that quantum mechanics is a correct description of reality on a micro scale. If there are limits to how correct it is, those are likely to involve questions about how to combine quantum mechanics and gravity, which we have so far been unable to do with a testable model.

Here is why I began with that preamble: one of the interesting challenges that quantum mechanics presents to us is that while the mathematical structure of it is clear, we aren鈥檛 entirely sure how to interpret what the equations are telling us. In other words, we can write down equations that make accurate predictions about experiments, but we aren鈥檛 always sure what that implies about what actually happened, physically, before any measurement occurs.

This may or may not be a problem. In the textbook I am using to teach this semester, Quantum Mechanics, Arjun Berera and Luigi Del Debbio : 鈥淏eyond any theoretical sophistication, a physical theory is first and foremost a description of natural phenomena; therefore it requires a very precise framework that allows the observer to relate the outcome of experiments to theoretical predictions.鈥�

From this perspective, quantum mechanics is incredibly successful. We have a theoretical framework 鈥� derived from the advanced mathematics of linear algebra 鈥� that allows us to determine what experimental outcomes we should expect.

Yet the microphysical world has all kinds of phenomena that we often describe as weird and out of sync with a classical, Newtonian picture. Consider the famed double-slit experiment in which a light beam is aimed at a plate with two parallel slits, behind which is a screen that detects the subsequent light pattern. First, the outcome of this experiment shows that light behaves like a wave and a particle simultaneously. Similar experiments with, for example, electrons display this same wave-particle duality. Second, the experiment set-up shows that a particle鈥檚 behaviour depends on whether we engage in the act of observing it or not. Third, and perhaps most jarringly, these outcomes also imply that particles don鈥檛 exist until we observe them.

In a , Lorenzo Catani, Matthew Leifer, David Schmid and Robert W. Spekkens named these three outcomes the 鈥渢raditionally regarded as problematic鈥�, or TRAP, phenomenology. The TRAP phenomenology forms the basis for our arguments that quantum mechanics is necessary. We simply cannot explain the phenomena using classical physics, we tell ourselves, our students and intrepid readers of publications like 快猫短视频.

But, as Catani, Leifer, Schmid and Spekkens pointed out, perhaps our inability to use classical physics to explain the TRAP phenomenology is a human failing and not proof that the universe is more complex than Isaac Newton imagined. In their paper, which is the subject of active debate, they developed a classical theory that can describe the TRAP phenomenology without reference to the quantum framework.

Importantly, the goal of these researchers isn鈥檛 to convince us that quantum mechanics is a wrong theory. Instead, they want scientists to do better when it comes to proving the claims we are making about how the universe works. Rather than simply arguing that experiments displaying apparent quantum behaviours require us to move to a quantum theory framework, scientists should prove that it is absolutely impossible to develop a theoretical framework using only classical ideas.

What they are talking about is the idea of a 鈥渘o-go theorem鈥�: a proposition that states a particular outcome is simply not possible. Physics is replete with such theorems, some of which are proven and some of which are still just ideas that may or may not be true. For example, in 1842, Samuel Earnshaw mathematically proved that a collection of charged (classical) particles won鈥檛 stay stable and motionless if the only force at work between them is the electric force. This is an example of a no-go theorem that has been proven.

There are other no-go theorems throughout theoretical physics that remain unproven hypotheses. And there is no rule saying that no-go theorems are a necessary feature of a good physical model.

Catani, Leifer, Schmid and Spekkens have raised a point that, until I read their paper, I had never really considered: are the boundaries we imagine for classical physics simply failures of imagination? If those boundaries are real, then we should be able to prove that a quantum framework is necessary.

Chanda鈥檚 week

What I鈥檓 reading

I鈥檓 still working through the Taylor Branch trilogy about Martin Luther King Jr.

What I鈥檓 watching

Like many people, I spent an hour watching a hold screen on Netflix while waiting for the liveLove is Blind reunion. Wah wah.

What I鈥檓 working on

I am thinking deeply about how I want to spend my time this summer.