RECENT ARTICLES

Philosopher Jenann Ismael invokes the thermodynamic arrow of time to explain how human intelligence emerged through culture.

Grounded physicists are exploring the use of online and virtual-reality conferencing, and AI-controlled experiments, to maintain social distancing. Post-pandemic, these positive innovations could make science more accessible and environmentally-friendly.

Untangling how the human perception of cause-and-effect might arise from quantum physics, may help us understand the limits and the potential of AI.

Physicists are using optogenetics techniques to make a rudimentary agent, from cellular components, which can convert measurements into actions using light.

Investigating how quantum memory storage could aid machine learning and how quantum interactions with the environment may have played a role in evolution.

FQXI ARTICLE

September 23, 2020

Usurping Quantum Theory

The search is on for a fundamental framework that allows for even stranger links between particles than quantum theory. It could lead us to a theory of everything.

FQXi Awardees: Miguel Navascués

June 28, 2018

Miguel Navascués

IQOQI, Vienna

Fast-forward to today and quantum physics still dominates Navascués’s working life at the Institute for Quantum Optics and Quantum Information in Vienna, Austria. Except now he’s trying to destroy the very theory that inspired him, looking for concepts to replace quantum physics. It may sound crazy, at first, but it fits with the history of physics, he notes, in which theories, like kings, are often usurped. "Every theory proposed so far to describe the universe has been refuted," Navascués says. It happened with Aristotelian physics, the geocentric model of the solar system, and the Newtonian theory of gravity, to name but a few. "One day, somebody will conduct an experiment that will not have an explanation in terms of quantum theory," he adds.

One day, somebody will

conduct an experiment

that will not have an

explanation in terms

of quantum theory.

conduct an experiment

that will not have an

explanation in terms

of quantum theory.

- Miguel Navascués

The arena that Navascués is exploring is that of quantum correlations, something he explains using two oft-used characters, Alice and Bob. Each has a quantum lab for measuring particle properties, such as its speed, or whether it moves left or right. A correlation manifests as Alice and Bob’s results being linked. Perhaps every time Alice’s particle moves to the right so does Bob’s. "Ultimately, there must have been some connection between Alice and Bob before they conducted the experiment," Navascués says. "Otherwise there shouldn’t be any correlation between the labs."

Roll of the Dice

These correlations don’t necessarily have to be quantum. Say Alice and Bob choose which result to announce based on dice that you had rolled before hand. By distributing the result of your roll to both parties, you correlate their results, and there’s nothing particularly mysterious about that. But the quantum world is different and a bit stranger. Imagine creating two quantum particles in the same place and passing one to Alice and the other to Bob to experiment on and produce a measurement. Those particles might exhibit the properties of entanglement: change the quantum state of Alice’s particle and Bob’s instantly changes too. Some of those correlations cannot be explained using everyday "classical" physics.

The set of quantum correlations is actually greater than the set of classical correlations, with the latter being a particular sub-set of the former. And just as quantum theory usurped classical theory, Navascués hopes to topple quantum theory by finding an alternative that, in turn, has a greater set of correlations, but that still contains those of quantum theory within it. Three years ago he made a breakthrough. "We call it the ’almost quantum’ set," he says. "It contains correlations and outcomes not possible within quantum theory." They cannot be explained as the equivalent of creating two quantum particles in the same place and passing one to each experimenter, which is how entanglement is usually understood to be created. In recent work, Navascués and colleagues have identified a way to distinguish conventional quantum correlations from almost-quantum correlations (Belén Sainz et al.,

Confusing Correlations

Will a future laboratory test reveal weird links between particles that validate

’almost quantum’ theory?

But quantum theory has been around for over a century, so, if Navascués is right, why haven’t we seen a trace of behaviour beyond it yet? "Perhaps we don’t know how to make the proper measurements or we don’t know how to prepare the particles in the right way," he says. Most of the experiments people have done in this area rely on photons—particles of light. "Quantum mechanics is a theory that was built for photons," notes Navascués. "Perhaps if you start conducting weird measurements, with more exotic particles, you might get results beyond what quantum theory predicts."

"I find his work very intriguing, and I have been fascinated by it since hearing it for the first time a few years ago," says Gerardo Adesso, a mathematical physicist at the University of Nottingham, UK. It "leaves room for a little more beyond quantum theory. This little more is still far from being formalised and understood, both mathematically and physically, but some surprising connections with certain approaches to quantum gravity make Miguel’s approach even more plausible." Adesso adds that what’s needed is an experiment that might falsify or validate Navascués’s ideas, but that might take fifty years.

"What Miguel and colleagues did was thought-provoking," says Marco Piani, from the University of Strathclyde. But he adds that the approach’s weakness is that, so far, it only deals with correlations. It may be easier to infer the underlying theory if Navascués was able to include other quantum properties in the analysis. "Nonetheless, it is clear that we can learn a lot in the process of trying, and the work by Miguel and colleagues is certainly an important contribution."

Comment on this Article

Please read the important Introduction that governs your participation in this community. Inappropriate language will not be tolerated and posts containing such language will be deleted. Otherwise, this is a free speech Forum and all are welcome!

function ValidatePostText_main () {
form = document.addPostForm_main;
var recaptcha = $("#g-recaptcha-response").val();
if (recaptcha === "") {
event.preventDefault();
alert("The reCaptcha Box below must be checked before you submit the form");
}
else if (form.postText_main.value == '') {
alert ("The post contains no text");
return false;
}
else {
return true;
}
}

**Your name:**
(optional)

Recent Comments

read all article comments

Please read the important Introduction that governs your participation in this community. Inappropriate language will not be tolerated and posts containing such language will be deleted. Otherwise, this is a free speech Forum and all are welcome!

Please enter the text of your post, then click the "Submit New Post" button below. You may also optionally add file attachments below before submitting your edits.

HTML tags are not permitted in posts, and will automatically be stripped out. Links to other web sites are permitted. For instructions on how to add links, please read the link help page.

You may use superscript (10

^{100}) and subscript (A_{2}) using [sup]...[/sup] and [sub]...[/sub] tags.You may use bold (

**important**) and italics (*emphasize*) using [b]...[/b] and [i]...[/i] tags.You may also include LateX equations into your post.

Insert LaTeX Equation
[hide]

LaTeX equations may be displayed in FQXi Forum posts by including them within [equation]...[/equation] tags. You may type your equation directly into your post, or use the LaTeX Equation Preview feature below to see how your equation will render (this is recommended).

For more help on LaTeX, please see the LaTeX Project Home Page.

LaTeX Equation Preview

preview equation

clear equation

insert equation into post at cursor

LaTeX equations may be displayed in FQXi Forum posts by including them within [equation]...[/equation] tags. You may type your equation directly into your post, or use the LaTeX Equation Preview feature below to see how your equation will render (this is recommended).

For more help on LaTeX, please see the LaTeX Project Home Page.

LaTeX Equation Preview

preview equation

clear equation

insert equation into post at cursor

Attachments
[hide]

You may optionally attach up to two documents to your post. To add an attachment, use the following feature to browse your computer and select the file to attach. The maximum file size for attachments is 1MB.

Once you're done adding file attachments, click the "Submit New Post" button to add your post.

You may optionally attach up to two documents to your post. To add an attachment, use the following feature to browse your computer and select the file to attach. The maximum file size for attachments is 1MB.

Once you're done adding file attachments, click the "Submit New Post" button to add your post.

STEVE DUFOURNY wrote on August 4, 2018

Hi Joe, thanks for this advice , :) regards

Hi Joe, thanks for this advice , :) regards

JOE FISHER wrote on August 3, 2018

Dear Steve,

You are never going to get better until you become capable of grasping reality. Please stop attempting to deal with finite misinformation about invisible space/time.

Joe Fisher. Realist

Dear Steve,

You are never going to get better until you become capable of grasping reality. Please stop attempting to deal with finite misinformation about invisible space/time.

Joe Fisher. Realist

JOE WILLIAM FISHER wrote on August 3, 2018

Dear CLAUDE MICHAEL CASSANO,

The earth had a visible surface for millions of years BEFORE you published your senseless mathematical guesswork, It logically follows that Nature must have devised the only real visible structure of the Universe allowable. There has only ever been one real visible infinite surface eternally occurring in one infinite dimension that am always mostly illuminated by finite non-surface light.

Joe Fisher, Realist

Dear CLAUDE MICHAEL CASSANO,

The earth had a visible surface for millions of years BEFORE you published your senseless mathematical guesswork, It logically follows that Nature must have devised the only real visible structure of the Universe allowable. There has only ever been one real visible infinite surface eternally occurring in one infinite dimension that am always mostly illuminated by finite non-surface light.

Joe Fisher, Realist

read all article comments