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Is optical quantum computation easier than we thought?

In my most recent paper (read it here), Tim Ralph and I demonstrate that a single-purpose optical quantum computer might be constructed much more easily than previously thought. In fact, building such a quantum computer is within reach of present-day technology. The paper extends recent results by Scott Aaronson & Alex Arkhipov, where they showed that a type of optical quantum computer, called a ‘BosonSampling’ computer, which is classically hard to simulate, can be constructed much more easily than ‘universal’ quantum computers (i.e. the most general type of quantum computer). Such a computer is ‘easier’ to build in the sense that no active switching, feedforward or memory is required – just single photon sources, passive linear optics and photo-detection (things that we can readily do in the lab).

In our work we demonstrate that even with very substantial loss rates (whether it be source inefficiency, loss within the circuit, or detector inefficiency), such a computer can likely perform calculations beyond the reach of any classical computer. This is great news for experimentalists, for whom photon loss is a killer in their experiments. Our results show that with enough single photon sources, even with a loss rate of 50% our optical quantum computer can likely do things that classical computers can’t. This is unlike fault-tolerance results for universal quantum computers, whereby loss rates of even 0.1% are a killer. This all sounds very optimistic, but there is one drawback – no one knows what to do with this particular type of quantum computer. Aaronson & Arkhipov show that such a device almost certainly can do things that a classical computer can’t, but no actual applications have been identified. So there’s a catch – building such a quantum computer, which can outperform all the classical computers in the world put together, is within reach of present-day technology, but, no one has any idea what to do with it.

I hope these results will stimulate further research into Aaronson & Arkhipov-type devices, which will hopefully come up with some useful applications – a killer application for BosonSampling would represent a major step forward for the field. In the meantime, I hope some of the experimental groups in the optical quantum computation community will think about elementary demonstrations of such systems. Simple extensions of present-day multi-photon quantum walk experiments (e.g. this work by Peruzzo et al., and this work by Owens et al.) could act as an elementary test-bed for such systems.

The region overlapped by red and blue is where we suggest a BosonSampling quantum computer is performing a classically intractable computation - plotted against the number of photon sources and the net single photon source/detection efficiency.

Unions – Vandals & Extortionists

The recent debacle with Qantas has rekindled my thoughts about the union movement in general. I firmly believe that unions are, in general, a negative influence on our society and many of their activities amount to blackmail and economic vandalism. While there are some legitimate roles for unions, such as providing advice to members and legal representation when the need arises, the bulk of contemporary union activity centres around industrial action, or, as I like to call it, extortion.

When someone gets a job at a business, they agree to do a certain amount of work for a certain amount of pay. It is not an agreement entered into solely on one side. It is not an agreement forced onto one side by the other. It is a voluntary, mutual agreement. I find it outrageous that, after entering an agreement voluntarily, that one side (in this case the unions) retrospectively decide that actually, on second thought, they want more than they agreed to. Then, to achieve that aim, they engage in strike action, with the aim of blackmailing the business by threatening them with bankruptcy if they don’t acquiesce. This is extortion.

Imagine that you hired someone to help clean your house, and you agreed to pay them $10 an hour to help you out. Then, a few weeks later they turn up outside your house with a bunch of mates, threatening signs and refusing to work unless you agree to $20 an hour. Would you (a) give them $20 an hour, or (b) fire them an hire someone else who is willing to do the work they agreed to do? This example precisely reflects what’s happening in the union movement around the world.

You might say, why not give them $20 an hour – they’d be better off, it’s only fair? The answer is, simply, that it drives unemployment. Why employ one person for $20 an hour when you can employ two for $10? Thus, the activities of unions effectively act as a driving force for unemployment.

Those in support of unions frequently claim that unions are there to represent workers. This couldn’t be further from the truth. Unions do not represent workers, they represent paying members. Therefore, those who are not represented by the unions, and I’m specifically referring to the unemployed, get no representation whatsoever and lose out. I’d rather have solidarity with someone who is unemployed and priced out of a job, than someone with a job and a comfy lifestyle, who simply wants more.

Indeed, it is questionable whether union activity even benefits the members. When people earn more money without a corresponding increase in productivity, people have more money with which to buy goods, but the amount of goods hasn’t changed. This is inflation. When inflation occurs the RBA responds by increasing interest rates, which means that everyone is paying more on their mortgage, more on their car loan, more on their credit card, and no one is better off.

Some hardline critics of unions advocate banning unions as a solution to the problem. This solution involves taking away people’s freedom of association. So, how do we prevents these kinds of activities without taking away freedom? By giving more. Specifically, employers should be allowed to discriminate against employees on the basis of union membership. They should have the right to say “we’ll employ you, provided that you don’t join the union and engage in strike action”, and negotiate these terms into the employment contract. Secondly, because industrial action amounts to extortion, employers should be free to fire employees engaging in that kind of action and litigate for losses. This solution addresses the problem, without depriving anyone of inalienable rights.

I hope the outcome with Qantas strengthens the public’s skepticism of the union movement and opens people’s eyes to the true nature of collective action. It’s time society recognised the true face of unions. They are not there to help people out or make sound economic decisions. They are there to accumulate power into the hands of union bosses and thugs so they can later run for public office and become a minister (or undemocratically overthrow a Prime Minister). This needs to stop.