Quantum Science 101

Introducing quantum science to an audience unfamiliar with the strangeness of the invisible quantum micro-world is a fool’s errand for anyone but the most brave and knowledgeable. As Richard Feynman (Nobel Prize in Physics 1965) famously stated: „I think I can safely say that nobody understands quantum mechanics“.

Yet this was the task William D. Phillips and Serge Haroche (Nobel Prize in Physics 1997 and 2012, respectively) set themselves for their Agora Talk on day 3 of #LINO70. From a live poll at the start of their lecture, ~45% of the audience had no physics background at all.

A Brief History of Quantum

Haroche was first up, setting the stage by taking the audience on a whirlwind journey through the history of quantum science. He divided this into three eras:

• the birth of quantum science from 1900–35 when the founding fathers of quantum mechanics were penning the strange rules that govern the quantum realm and hotly debating different interpretations of quantum theory
• the ‘Shut up and calculate!’ period from 1935–85 “during which the debate about the interpretation of quantum theory was put aside” and scientists decided to use the theory to explain the micro-world to spectacular effect
• and the time from 1985 to today, when physicists have been manipulating isolated quantum systems and starting to build applications in areas such as quantum computing, quantum communication and quantum metrology.

Now, around 100 years after the phrase ‘quantum mechanics’ was first coined by Max Born, Werner Heisenberg and Wolfgang Pauli (Nobel Prize in Physics 1954, 1932 and 1945, respectively), striving to build these quantum applications has brought quantum physicists full circle, reviving many of the debates surrounding the fundamentals of quantum theory.

“It’s an interesting question to ask oneself whether we know and we understand more about these issues now than at the time [of the founding fathers],” ended Haroche. Handed the baton, Phillips couldn’t leave this question hanging in the air, providing an appropriately quantum response: “The answer to that is both ‘yes’ and ‘no’,” he said. “We understand [quantum theory] so well that we can calculate some things to 10 decimal places, and we understand it so little that it challenges our very ideas of what reality is.”

Somehow over the course of 10 minutes, Phillips managed to explain exactly how quantum mechanics challenges our notions of reality through the quantum concepts of superposition and entanglement in a clear and engaging way, even having time to fit in a description of how quantum computers work and what they can bring to society.

Hitting the Books Early?

Finishing their talks with plenty of time to spare left space for a fascinating Q&A with the audience spanning a huge range of topics. Haroche and Phillips were quizzed on their thoughts on the various interpretations of quantum mechanics, why we need quantum computers to simulate quantum systems and whether quantum founding fathers Niels Bohr, Albert Einstein and Erwin Schrödinger (Nobel Prize in Physics 1922, 1921 and 1933, respectively) would be surprised by the state of quantum physics today.

One of the most interesting questions came from young scientist Max Carey who asked whether exposing minds to quantum concepts at a younger age than currently could help them grapple with the mysteries of quantum theory in later life.

“We often see today that students come to university with less of a difficulty thinking about quantum problems than was the case perhaps 40 years ago,” responded Phillips. However, he warned that “one of the problems is that our students today are often better at understanding quantum mechanics than they are classical mechanics.”

Both Haroche and Phillips put this down to the rise of screen time and fall of children and students playing and interacting with the physical world. “I think that children have less contact with reality is very worrisome,” added Haroche. So, although neither speaker agreed that quantum mechanics should be taught at an earlier age, they both stressed the need for more focus on basic mathematical and mechanical understanding if society is going to churn out the quantum physicists that industry is crying out for.

Having been treated to an entertaining and informative tour of quantum science, the session ended on a positive note for young scientists to take away. “There are a lot of questions that need to be solved by basic research, and whatever comes out of it will be fascinating… maybe we will find something even more astonishing than the quantum computer,” said Haroche, before Phillips concluded: “This is a great time to be a physicist and it’s a great time to be thinking about and working on these kinds of problems – we should be grateful for that.”