In a recent podcast, “Enrique Blair on quantum computing,” Walter Bradley Center director Robert J. Marks talks with fellow computer engineer Enrique Blair about why quantum mechanics is so strange but important to our future. They discussed the prospects of slowing down quantum computing to make it more useful (adiabatic computing).
The discussion of quantum communication begins at approximately 58:47. The Show Notes and transcript follow.
Enrique Blair (pictured): I guess the challenge with entangling massive numbers of quantum systems is that entanglement becomes much more fragile. In quantum communication, you just need pairs of photons to be entangled. One with another, that’s it. Whereas with quantum computing, you need many, many systems to be entangled, and that’s just very fragile.
Robert J. Marks: Okay. Look in your crystal ball. What is the future of quantum computing and quantum communication? Is this something we’re going to achieve or is this something we’re just going to chip away at for a long, long, long time and find out that the engineering, at least to the degree that we would like it to perform, is not possible?
Enrique Blair: Quantum communication is much closer and a much easier problem… The challenge with so many qubits entangled is that it’s very hard to maintain that entanglement for any useful amount of time. Right now, the state of the art is maybe 70 qubits entangled, 50 qubits entangled. We have a long, long ways to go before we can do the practical things that everybody dreams about with quantum computing.
Now, that said, there are other applications that are maybe closer at hand. There’s a different kind of quantum computing called adiabatic quantum mechanics. It goes back to the adiabatic theorem.
The idea is that if you evolve a quantum system slow enough, you can maintain the system in its lowest energy configuration. The promise of adiabatic quantum computing is that we can solve optimization problems there. Because in classical computing, there’s no guarantee. When you attack an optimization problem, there’s no guarantee that you’re finding the absolute or the global minimum.
Now with adiabatic quantum computing, you can evolve the system from an input state to a solution state slowly enough that in theory, you can be guaranteed to find the global minimum. This is actually already being done. There’s a company called D-Wave and they have 2,000 qubits working together.
Note: “3.8 Adiabatic Theorem The adiabatic theorem, originally proved in Born and Fock (1928), has important applications in quantum computing (Section 4.3 and Chapter 14). An adiabatic process changes conditions gradually so as to allow the system to adapt its configuration. If the system starts in the ground state of an initial Hamiltonian, after the adiabatic change, it will end in the ground state of the final Hamiltonian.” – Peter Wittek, “Adiabatic Theorem”Quantum Mechanics
Robert J. Marks: How many did IBM have, 53 or something?
Enrique Blair: Yeah. We’re talking 50 to 70. The reason they have 2,000 cubits working together and IBM and Google don’t have that much is, we’re talking about two different computational paradigms. One, in the adiabatic world, you don’t need as much entanglement between all of the cubits. And so you don’t have that fragile entanglement.
Robert J. Marks (pictured): Well, I think that we’re going to have quantum computing. But it seems to me, having not cracked the problem for the last 30 or even more years, that there has to be innovation which comes forward. I think that the best technology has been thrown at it, and there needs to be some sort of breakthrough. Well thank you, Dr. Blair!
Here are the earlier discussions:
How spooky “quantum collapse” can give us more secure encryption. If entangled photons linked to random numbers are transmitted, parties on either end can know, via high error rates, that they’ve been intercepted. Secure quantum encryption may be more practical than general quantum computing because it needs only a few entangled particles, not many, to succeed..
Why Google’s “quantum supremacy” isn’t changing much—not yet. Quantum computing was suggested by physicist Richard Feynman in 1982; the supremacy battles are quite recent. While Google and, more recently, Chinese scientists, have achieved remarkable computing feats, practical uses are still under development.
How quantum computing can and can’t help us here in Macro World. Quantum computing could easily break down current encryption schemes. Quantum computing can help us create much safer encryption in exchange but currently it requires very cold temperatures in order to work.
“Spooky action at a distance” makes sense— in the quantum world. Einstein never liked quantum mechanics but each transistor in your cell phone is a quantum device. The fact that the spooky quantum world is real means that quantum computing could greatly reduce computers’ drastic environment impact.
The final ambiguous truth about Schrödinger’s cat. Schrödinger came up with the cat illustration to explain quantum mechanics to interested people who were not physicists. We don’t see quantum paradoxes outside the lab because everything we see consists of far too many quantum subsystems for any one particle to stand out.
How scientists have learned to work with the quantum world.
It’s still pretty weird, though. Wave function mathematics can work with particles that may be in different places (quantum superposition). QM can also generate truly random numbers we can use.
Here’s why the quantum world is just so strange. It underlies our universe but it follows its own “rules,” which don’t make sense to the rest of us. Computer engineer Enrique Blair explains to Robert J. Marks the simple experiment that shows why so many scientists find the quantum world “mind-blowing.”
- 00:54 | Introducing Dr. Enrique Blair, a professor of electrical and computer engineering at Baylor University
- 03:08 | The history of quantum mechanics
- 13:16 | Quantum superposition
- 21:50 | Schrödinger’s cat
- 27:45 | Why didn’t Einstein like quantum mechanics?
- 28:51 | Quantum entanglement
- 32:58 | Applications of quantum mechanics
- 34:53 | Quantum dots
- 37:31 | Quantum computing
- 43:48 | The use of quantum computers
- 47:55 | Quantum supremacy
- 55:32 | Quantum communication
- 58:47 | The future of quantum computing
- Enrique Blair’s website
- Copenhagen Interpretation of Quantum Mechanics at Standford Encyclopedia of Philosophy
- Young’s double-slit experiment at Encyclopædia Britannica
- Planck’s explanation of black-body radiation at Encyclopædia Britannica
- Quantum superposition at Wikipedia
- Nobel Prize in Physics 1932 — Werner Heisenberg
- Nobel Prize in Physics 1933 — Erwin Schrödinger
- Many-Worlds Interpretation of Quantum Mechanics at Stanford Encyclopedia of Philosophy
- Schrödinger’s cat at Wikipedia
- Quantum entanglement at Wikipedia
- Quantum bit (qubit) at Wikipedia
- Quantum dots at Wikipedia
- Shor’s algorithm at Wikipedia
- RSA at Wikipedia
- Grover’s algorithm at Wikipedia
- Quantum supremacy at Wikipedia
- IBM on Google’s claim of quantum supremacy
- Quantum communication at MIT Technology Review
- Adiabatic quantum computation at Wikipedia