Quantum Bayesian Networks

March 4, 2011

The Greatest Obstacle to Building a Quantum Computer

Filed under: Uncategorized — rrtucci @ 1:12 am

In my opinion, the greatest obstacle to building quantum computers is not Nature, which seems to be quite willing to allow us to build them. It’s the lamentable, needless obstacles that American society is placing in front of those who would love to build them. Aaron O’Connell’s current situation illustrates this point. Aaron, after doing some prize-winning QC work, may end up working at a job that will not tap his expertise and proven talent in QCs and experimental physics.

Check out:

Quantum Physicists “Depressed” and “Isolated,” Says Acclaimed Quantum Physicist
by Anya Kamenetz (Fast Company, March 4, 2011)


Yesterday Aaron O’Connell stunned TED audiences with his description of an experiment three years in the making that for the first time showed quantum delocalization taking place at the level of a physical, visible object. In other words, for his PhD thesis, he got a very small piece of aluminum to be in two places at once. 

When I caught up with the young, spiky-haired O’Connell I congratulated him on this achievement, but he surprised me by sounding pretty dejected. “My nametag says ‘freelance,’” he pointed out. “That’s what you say when you’re unemployed.” O’Connell revealed that he’s considering starting a tech company, maybe to build iPhone apps. “I just want to be around people,” he said, a funny statement for someone who had just shared his discovery with a potential audience of millions. “If you go into any physics lab everybody is depressed and feels isolated. We don’t get any feedback that anybody cares about what we’re doing.”

I mentioned O’Connell’s work before in the following blog post:

Quantum Computing’s American Riviera



  1. Do you think Optical Computing will happen first. Many of the ‘obstacles’ (like wave interference) are similar but less extreme in Optical Computing, and so are the benefits similar but less extreme (massive parallelism, speed). So it would seem to me to be a natural stepping stone, and when we hit the limits of Optical COmputing people will move on to Quantum Computing.

    Comment by Charles Armstrong — March 9, 2011 @ 12:33 pm

  2. Hi Charles,
    I don’t know too much about optical computing, but from the little I’ve read, my impression is that it will complement quantum computing rather than replace it. All-optical computing has at least two physical limitations that I know of:

    1. Difficulty in miniturizing photon devices (X rays < 10 nm, UV <400 nm, 1 atom ~ 0.5 nm)
    2. It seems that one needs more power and generates more heat when operating an optical nonlinear device than when operating an electron nonlinear device that does the same thing. Shot noise(i.e. statistical fluctuations in the photon number) of photon devices leads to more power dissipation than thermal noise of electron devices. That’s because when two light modes interact nonlinearly, electrons act as middlemen of the interaction. So optical devices in a sense compound the noise problem by putting shot noise on top of the thermal noise of the mediating electrons. More noise implies more power dissipation. Also the higher the noise, the higher the power you need to operate at in order to hold down the error rate to almost zero, according to information theory.

    Comment by rrtucci — March 9, 2011 @ 8:46 pm

  3. Aaron O’Connell’s TED2011 talk can now be viewed on YouTube

    There is also a Wikipedia entry for him (probably made by his proud mom).

    Comment by rrtucci — June 7, 2011 @ 5:51 pm

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