# Will Quantum Computing Enhance Analog Design? Part 1

In the discussion following Brian Bailey's blog, Operations per Joule, the subject of quantum computing came up. I posted a couple of links, one regarding a potential type of optical quantum computer called a Boson Sampling Computer, one about Google’s interests in quantum computing.

Quantum computers are viewed as being superior for certain kinds of problems, for example where there are many possible paths. Consider Figure 1, a schematic representation of a network of water pipes. (Note: Analogies to acoustic systems or fluid dynamic systems are often used to convey general concepts in electrical and RF systems — just don't push the analogy too far!) The water entering each pipe at the top (from the faucets) can take many possible paths to reach the pipes leaving the bottom.

Figure 1

Calculating the flow rate exiting at the bottom given the rates from each faucet at the top is hard (left diagram), but doable with existing computers. Calculating the paths of every molecule is much harder, but a quantum computer might do it in seconds.
(Source: EAF LLC)

A similar problem has been solved for photons in an optical network using the Boson sampling method mentioned in the first paragraph. A waveguide network used for Boson sampling is shown schematically in Figure 2.

Figure 2

Schematic representation of a network of waveguides created in silica.
(Source: “Experimental boson sampling”, Nature Publishing Group, 1749-4893, http://dx.doi.org/10.1038/nphoton.2013.102; used with permission of the author)

Boson sampling is similar to analog computing, where a physical configuration of the computer solves certain problems. In the boson sampling case, a pattern of waveguides is created in silica using lasers, then used to solve for the photon distribution exiting the pattern.

A traditional digital computer would calculate values of equations at every point of a mesh representing the interior space of the network of pipes, and iterate to find a steady state solution. We could use that solution to determine how much water would come out of each bottom pipe, given flow rates entering at the top.

Now suppose we wanted a solution at the particle level — i.e., we want to follow every molecule of water from start to finish. While, in principle, we could do that using statistical models with the bulk equations, the problem would quickly use up all the computing power we have. For a large-enough network, it would become impossible to solve in a reasonable time.

A quantum computer (one using quantum bits, or qubits, not the boson sampling method noted earlier), on the other hand, could calculate the position and velocity of every molecule, by investigating all possible states simultaneously . It is this inherent parallel computing property that gives quantum computing so much promise. Other problems of this sort include simulation of communication and road networks, and mimicking the human brain for artificial intelligence.

In Part 2, we will continue to look at quantum computing and consider the comparison to analog computing.

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## 7 comments on “Will Quantum Computing Enhance Analog Design? Part 1”

1. SunitaT
May 31, 2013

@Blaine, thanks for the post. Quantum computing promises faster solution to some problems. Already some commercial versions of Quantum computers (D-Wave) is available in the market. Looking forward for your next blog to learn more about quantum computing.

2. eafpres
May 31, 2013

Hi Sunita–thanks for reading the blog.  I think you will find Part II interesting.

3. Davidled
June 1, 2013

I thought that Quantum Computing has been developed and researched for a while in the IBM, HP, Intel and etc. D Wave is specialized for a specific customer such as Government.  To commercialize the product in public, cost will be one of main factor in the market.  There is no doubt that in theory, quantum computing is awesome.

4. eafpres
June 1, 2013

Hi DaeJ:  Well, IBM and many universities and research groups are working on various aspects of quantum computing.  Intel, however says they are not doing so yet.  You might be interested in this article (free registration required):

Seeking Alpha Quantum Computing and Intel

I don't agree with your characterization of D-Wave.  They are a small company with venture capital funding.  Due to the specialized nature of Quantum Computers, very few labs could even use one, so it is natural to expect the first customers to be government or university labs.  D-Wave sold an early D-Wave 1 to Lochkeed Martin who is using it to study various areas, including how to analyze complex systems like aircraft during the design phase.

As noted in my blog, D-Wave just sold a D-Wave 2 to the Quantum Artificial Intelligence Laboratory which is funded by Google, uses space donated by NASA, and will be operated by the Universities Space Research Assocation (USRA).  Some of the time will be monopolized by Google and USRA, the rest will be offered to reserach groups.  So it is a combination of private and public but the funding is definitely not government.  It makes perfect sense that Google would want to be at the forefront of Quantum computing; eventually quantum computers might make computer speech recognition and response very human, they might improve search in large databases, and many other things of direct interest to Google.

You are correct that cost is a big barrier, but in the near future there won't be too many quantum computers and even when more commercialized, it is likely they may operate in the cloud and there will be no need to “put one on a desktop”.  Google of course is at the leading edge of cloud computing with their Chromebooks.  Just imagine if the cloud had quantum capability what a Chromebook might be able to do.

5. RedDerek
June 2, 2013

From my perspective, I would just ask, what would the simulation speed enhancement would be for a power supply design simulation? If my current simulation can take 12 to 16 hours, would Quantum computing allow me to run the same simulation in 12 to 16 minutes? Then being able to share processor time on the cloud would get us back to the data centers of the 1980's where one was charged for the processor time to run one's program.

6. eafpres
June 3, 2013

Hi RedDerek–I think your question will be answered, at least in part, in Part 2.

The detailed answer depends on the exact problem type.  I think (but am not 100% sure) that problems of the type “Here is an analog system (say, power supply) that has these ranges of values for inputs and various components.  What is the optimum value for component x?” may be well suited to quantum computers becuase in principle a quantum computer could look at all the ranges of the inputs simultaneously (if there are enough qubits) and thus should be very fast at this type of optimizaton.

If you have more questions after part 2 we will go into it deeper.

7. amrutah
June 4, 2013

RedDerek,

I think it should take very less time for the simulation, not sure whether it would be in minutes.

In some tests it speed was found to be 3600 times a super computer, (yes a super computer), and for few tests it was 55000 times faster than the super computer.

You may want to check this.

Instead of using the binary  bits  0 and 1, it has 512 quantum bits, or qubits for interaction and decision making.

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