Search FQXi


Georgina Woodward: "Climate has had identifiable shifting patterns over thousands and over..." in Wandering Towards a Goal:...

John Cox: ""Do you have the slightest conception of the size of the earth or the..." in Wandering Towards a Goal:...

Georgina Woodward: "James, I'm sorry for getting the way you define mass wrong. It is clear to..." in Sounding the Drums to...

John Cox: "James, Now, please. Do not take umbrage. I fully accept covariance within..." in Sounding the Drums to...

ms office support: "There are many users of MS Office who use different applications of it for..." in Are We Merging With Our...

Samaira Khan: "Hi there, I enjoy reading through your article post. I like to write a..." in Retrocausality,...

Nitina oania: "" in Quantum Replicants:...

Nitina oania: "We below at Chikara Video Game" understand exactly what it resembles to..." in Quantum Replicants:...

click titles to read articles

Sounding the Drums to Listen for Gravity’s Effect on Quantum Phenomena
A bench-top experiment could test the notion that gravity breaks delicate quantum superpositions.

Watching the Observers
Accounting for quantum fuzziness could help us measure space and time—and the cosmos—more accurately.

Bohemian Reality: Searching for a Quantum Connection to Consciousness
Is there are sweet spot where artificial intelligence systems could have the maximum amount of consciousness while retaining powerful quantum properties?

Quantum Replicants: Should future androids dream of quantum sheep?
To build the ultimate artificial mimics of real life systems, we may need to use quantum memory.

Painting a QBist Picture of Reality
A radical interpretation of physics makes quantum theory more personal.

August 20, 2017

The End of the Quantum Road?
Caslav Brukner ponders whether we’ve already found the ultimate theory of nature, without realizing it.
by Bob Swarup
FQXi Awardees: Caslav Brukner
September 23, 2011
Bookmark and Share

University of Vienna
The philosopher Thomas Kuhn once described science as "a series of peaceful interludes punctuated by intellectually violent revolutions." To Kuhn, scientific progress was never a gradual accumulation of knowledge, but an endlessly repeating battle between established theories, such as Newtonian gravity, and younger upstarts, such as Einstein’s general relativity.

Kuhn’s influence has been profound—and it’s left some wondering whether physicists will ever find the much sought after Theory of Everything, or whether every theory we create will inevitably be overthrown by a deeper more fundamental theory. Now, Caslav Brukner at the University of Vienna in Austria is asking precisely this question about quantum mechanics. The theory stands as our most accurate description of nature and is fundamental to our understanding of chemistry, the development of modern technology, and our insight into the origins of our universe. Given its enormous success, have we already found our ultimate theory, without realizing?

In the video below, Brunker talks about classes of theories that may move beyond quantum theory, and whether the next theory will be crazier than quantum:

The germ of Brukner’s obsession with quantum theory goes back to his childhood. Born in Novi Sad, Serbia, in 1967, the young Brukner was always more interested in asking "why?" rather than "how?". He recalls being more excited about pondering the nature of time and what makes a watch tick, rather than taking it apart and putting it back together again. When his brother gave him a copy of What’s Going On in the Atomic Nucleus? by Vladimir Paar for his thirteenth birthday, there was no turning back.

"Over the years, I have learned that quantum physics is weird and eludes every attempt to be understood within a classical picture," says Brukner. "It is this weirdness that keeps my curiosity alive—like that of a child— and searching for answers to nature’s puzzles."

Brukner is now searching for those answers with the help of a $69,600 grant from the Foundational Questions Institute. At the heart of his research is the question of whether quantum physics provides the ultimate description of reality or whether there are other more fundamental theories lying in wait.

It is this weirdness
that keeps my curiosity
alive—like that of
a child.
- Caslav Brukner
Although quantum physics is extremely successful, some are troubled by its inherent randomness, which prevents us from predicting the behavior of quantum objects with certainty. According to standard interpretations, quantum objects do not have well-defined properties, until those properties are measured by an observer. Prior to observation, the particle exists in a superposition of many mutually exclusive states.

Some physicists find this quantum weirdness hard to stomach and hope to retrieve a classical concept of realism in which properties of the world about us exist regardless of whether or not we observe them. Einstein famously believed that particles contain extra properties, or hidden variables, that serve as blueprints, determining the particles’ behavior completely. If we knew what these hidden variables were, we could predict the fate of particles with certainty. But, asks Brukner, just how plausible is this concept of realism?

Quantum Overload

Brukner began to examine the features of quantum mechanics when he moved to Austria to pursue a Ph.D. at the Vienna University of Technology with Anton Zeilinger. Together, they realized that many weird quantum features could be explained by thinking about the information contained in a quantum system, just as computer scientists look at how information is encoded, stored, and transferred in bits. According to their approach to quantum mechanics, the most elementary quantum system, the qubit, carries one bit of information.

Should we accept quantum mechanics as the ultimate theory?
Or keep looking?

Credit: IQOQI, University of Vienna
Information theory, says Brukner, is the key to showing how plausible (or indeed implausible) it is that a deeper classical reality underlies quantum mechanics. It reveals that even within the simplest quantum system—an electron spin—classical realism is extremely resource demanding. That’s because it would take infinitely many hidden variables to encode all the instructions needed to explain the results of all possible measurements of the electron’s spin.

Brukner argues that the total information that can be carried by an electron spin is finite. That means, by necessity, the system’s answers to some questions will contain an element of randomness. Thus, Brukner and Zeilinger realized that the observed quantum behavior could be explained by nothing more mysterious than a lack of storage space for sufficient information.

One of the most
exciting questions for
physicists is: what
is our next theory?
- Caslav Brukner
Information theory can also be easily extended to naturally explain quantum entanglement—or "spooky action at a distance," as it was dubbed by Einstein. Entangled particles are inextricably intertwined, so that measuring one of them immediately changes the state of the other. This strange phenomenon has been confirmed many times in the lab, in quantum optics experiments (pictured above, right).

Brukner and Zeilinger have analyzed how information can be stored in an entangled system. For example, it would take two bits of information to jointly encode entanglement into two particle spins, so that they are parallel to each other. Once those two bits have been exhausted, there is no more storage space to encode extra spin information into either of the two entangled particles individually, says Brukner. As a result of this lack of extra encoded information, measuring the spin of one of the pair must yield a random value, while the spin of its partner will be immediately fixed, regardless of distance.

Final Theory?

Brukner’s work suggests that weird quantum properties such as superposition and randomness are here to stay—any theory that tries to get rid of them will fail to overcome this information limit. So, does that mean that quantum theory is the final theory? Should we now stop hunting for anything deeper? Not necessarily.

"One of the most exciting questions for physicists is: what is our next theory?" says Brukner. "The entire history of science has taught us accepted scientific theories are superseded by new ones, of which the old are special cases. It is therefore hard to believe that quantum theory is our final theory."

Although most proposed alternatives to standard quantum mechanics have steadily fallen by the wayside, Brukner believes that this is because they all tried—mathematically and conceptually—to save some part of the pre-quantum concepts of classical physics. Brukner, however, wants to study alternatives that preserve the seemingly bizarre properties of quantum mechanics. "I want to investigate those theories, which, like quantum theory, are intrinsically probabilistic, allow superposition and entanglement, but may still differ ."

Brukner is a very
deep thinker, who
believes in fundamental
connections between physics
and information.
- Vlatko Vedral
"Approaches to quantum theory where information is a basic concept and plays a crucial role are seemingly now in a revival period," says Thomas Durt, a quantum physicist at Vrije University Brussels, in Belgium. Durt believes new approaches are good because they lead to new insights. However, he adds that physicists are often less receptive to attempts to reconstruct working physical theories to explain observed facts.

Vlatko Vedral, a quantum physicist at the University of Leeds, UK, likes Brukner’s attempts to derive theories beyond quantum mechanics. "Brukner is a very deep thinker, who believes in fundamental connections between physics and information," says Vedral. "Herein lies the hope to go beyond speculation and arrive at some experimentally testable predictions, which is the main goal of physics and underpins its wonderful power to comprehend the world."

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!
  • 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 (10100) and subscript (A2) 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

Your name: (optional)

Important: In order to combat spam, please select the letter in this menu between 'B' and 'D':

Recent Comments

compass measure the speed of 20 400 km are limited edition 3333 pieces Both options Meaningful 18K rose gold and .

tech precision ceramic PremireQuartz 18K 4th quarter of last years 5 07 billion Raymond Weil Nabucco Va Pensiero Alarm .


At the speed of light, time stops. Then, a true time duration can be found as the period T of an EM wave.

On the other hand, the wave (assumed as being of the same nature) associated with a sub-luminal speed particle does not experience stopped time and therefore does not have a true per se period T. This variable T does not exist for the free associated wave. But when we interact with the particle, we cause a slight deceleration and the emergence of a wavelength and period T....

read all article comments

Please enter your e-mail address:
Note: Joining the FQXi mailing list does not give you a login account or constitute membership in the organization.