Download While the ramifications of quantum computers

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Thomas Capizzi
Intermediate English Composition
10/19/2016
The Feasibility of Quantum Computers
Computers have become an integral part of our lives, and similar to most technology,
have steadily improved since computers were developed. Their efficiency, processing power, and
speed have increased massively since their first development. There is a constant problem with
computers, however: how they process information. No matter how fast it is, a computer must
process things one instance at a time (or more depending on their number of cores, but still a
very finite amount of processes at once). This will remain an issue with standard computers as
long as they exist. However, there is a new type of computer in development that would
theoretically be able to bypass this issue: the quantum computer. Currently, people are trying to
develop quantum computers, but it is proving very difficult. This raises an important question:
how feasible are quantum computers, and how hard should we try to develop them?
Despite its name, the quantum computer is not very difficult to understand conceptually.
A computer stores information with bits (0s and 1s); information is assigned specifically to those
bits, and those bits alone. The computer uses the bits to remember, store, and recall information,
and contains a set amount of them. When all of the bits are used up, the computer runs out of
storage until space is cleared. A quantum computer would work much differently: while a
quantum computer would contain a finite amount of information as well (stored on qubits, pieces
of “quantum memory”), qubits would be infinitely more flexible than standard bits. The qubits
would be used very liberally and can all be used at once through superposition (a complex
quantum mechanic, basically using two “states” of the qubit at the same time).
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The end result of this would be both fascinating and troubling: quantum computers would
be able to complete extremely taxing problems and huge amounts of processes with ease,
completing the work much more efficiently than standard computers. A quantum computer
would be more comparable to a human brain, able to handle and solve multiple problems at once,
as well as processing information faster. It also has processing speed a human brain wouldn’t
have, providing the best of both human minds and computer processing.
Speaking of standard computers, quantum computers would ruin them. As Andy Majot
and Roman Yampolskiy put it, “With advancements in quantum computing happening almost
weekly it is time to examine the effects this new technology will have on society and current
computational systems. Specifically, cryptographic systems need to be carefully analyzed since
the introduction of quantum computational resources would render discrete logarithm and
factoring based cryptographic systems like those based on [RSA] and [ECC] algorithms woefully
obsolete. These algorithms are widely used in the form of digital certificates, message
encryption, and even physical authentication devices like [RFID] badges. With this technology
compromised by quantum computing, governments and other organizations would be able to
eavesdrop on private citizens with relative ease. This has the potential to cause a slew of rights
violations and atrocities leading to catastrophe” (Majot et al, 17). This is the one thing most
scientists agree on with quantum computers: their ability to destroy encryption. “A noteworthy
consequence for cryptology is the possibility of breaking public key cryptosystems such as RSA”
(Palma et al, 567).
Standard computers encrypt data with, well, encryption, using extremely long prime
numbers to “lock” information behind a very difficult to crack math problem. Standard
computers are only able to attempt one prime number problem at a time, meaning that it would
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take a very long time to crack the encryption. A quantum computer, however, could run through
all of the prime numbers at the same time, cracking the most solid form of encryption we have in
mere seconds. While quantum computers would be a massive improvement over standard
computers, they would have to be gradually phased in to allow both the government and citizens
to adequately prepare for them.
Quantum computers were conceptualized as far back as 1982, and suggested as a device
that could compute extremely complex problems and systems. “In 1982, Richard Feynman
suggested that an avenue for the tractable simulation of quantum systems would be to build
quantum mechanical simulators. The most versatile quantum simulator is a universal quantum
computer—a device that uses quantum systems themselves to store and process data. It has been
proposed that a quantum computer can simulate many-body physical quantum systems (such as
molecules) and calculate their energies to a fixed accuracy with a number of quantum
computational resources that increases only polynomially with the number of particles. Such a
device would provide an extremely powerful tool for new science and technology because
essentially exact (within a specified basis) molecular properties would be available” (Lanyon et
al, 106). Not only would quantum computers make tracking extremely complex systems much
easier (or even possible at all), it might redefine the field as a result, allowing scientists to make
previously impossible developments and acquire new knowledge as a result.
While the ramifications of quantum computers would be significant, it is possible they
are still very far away. Quantum computers are mostly theoretical at the moment, and could have
very real issues to prevent them from becoming a consumer item, or even an item at all. For
starters, anything involving quantum mechanics is most likely unstable, and quantum computers
are no exception.
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Gil Kalai writes, “The main concern regarding the feasibility of quantum computers has
always been that quantum systems are inherently noisy: we cannot accurately control them, and
we cannot accurately describe them…What is noise?... Noise refers to the general effect of
neglecting degrees of freedom, namely, approximating the process on a large Hilbert space by a
process on a small Hilbert space. For controlled quantum systems and, in particular, quantum
computers, represents the controlled part of the system, and the large unitary process on
represents, in addition to an “intended” controlled evolution on, also the uncontrolled effects of
the environment” (Kalai, 510).
Essentially, quantum systems come with an inherent downside for using them:
unpredictability. While people attempt to find ways to compensate for and avoid it,
unpredictability is a default issue that would come with quantum computers, and it is entirely
possible people would be unable to find a workaround for it.
Kalai continues with the two most current hypotheses for the viability of quantum
computers: as he calls them, the optimistic hypothesis and pessimistic hypothesis. “The quantum
computer puzzle is, in a nutshell, deciding between two hypotheses regarding properties of noisy
quantum circuits: the optimistic hypothesis and the pessimistic hypothesis. Optimistic
Hypothesis: It is possible to realize universal quantum circuits with a small bounded error level
regardless of the number of qubits. The effort required to obtain a bounded error level for
universal quantum circuits increases moderately with the number of qubits. Therefore, largescale fault-tolerant quantum computers are possible. Pessimistic Hypothesis: The error rate in
every realization of a universal quantum circuit scales up (at least) linearly with the number of
qubits. The effort required to obtain a bounded error level for any implementation of universal
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quantum circuits increases (at least) exponentially with the number of qubits. Thus, quantum
computers are not possible” (Kalai, 510).
Computer scientists are torn between these two viewpoints. At this point, both are equally
valid (fitting for a quantum problem): there isn’t enough information available for either theory
to be proven without a shadow of a doubt. While prototype quantum computers have been
created, they aren’t far enough in development to provide a definitive answer either way. Both
hypotheses are based on how we are able to develop the quantum computers on a wider scale,
which we don’t know yet. Although quantum computers will technically be possible regardless
of which viewpoint is correct, depending on which hypothesis is accurate, their success will
wildly vary. If the optimistic hypothesis is true, quantum computers could very well become
widespread and portable, and possibly even a consumer item like personal computers are today.
If the pessimistic hypothesis is true, quantum computers will be severely limited, and have
relatively limited uses (or won’t even be developed enough for any uses).
Kalai extends on the ramifications of both hypotheses in detail. “It is often claimed that
quantum computers can perform certain computations that even a classical computer of the size
of the entire universe cannot perform! Indeed it is useful to examine not only things that were
previously impossible and that are now made possible by a new technology but also the
improvement in terms of orders of magnitude for tasks that could have been achieved by the old
technology. Quantum computers represent enormous, unprecedented order-of-magnitude
improvement of controlled physical phenomena as well as of algorithms” (Kalai, 512).
Kalai predicts that, if the optimistic hypothesis is true, technology as we know it will
change as drastically, if not more than, when the first computers were developed. Quantum
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computers would be able to solve problems much too complex for a standard computer to
process. The sheer amount of extra processing capability will make standard computers obsolete
in a variety of areas and redefine the limits of computers in general.
Kalai also notes, however, that this is exactly why he doesn’t believe in the
optimistic hypothesis. “I regard the incredible consequences from the optimistic hypothesis as
solid indications that quantum supremacy is “too good to be true” and that the pessimistic
hypothesis will prevail. Quantum computers would change reality in unprecedented ways, both
qualitatively and quantitatively, and it is easier to believe that we will witness substantial
theoretical changes in modeling quantum noise than that we will witness such dramatic changes
in reality itself” (Kalai, 513).
Recent developments have indicated that the optimistic hypothesis is at least plausible,
beginning as early as 2001. “In 2001, all-optical quantum computing became feasible with the
discovery that scalable quantum computing is possible using only single-photon sources, linear
optical elements, and single-photon detectors. Although it was in principle scalable, the massive
resource overhead made the scheme practically daunting. However, several simplifications were
followed by proof-of-principle demonstrations, and recent approaches based on cluster states or
error encoding have dramatically reduced this worrying resource overhead, making an all-optical
architecture a serious contender for the ultimate goal of a large-scale quantum computer”
(O’Brien, 1567). While quantum computers weren’t actually in development at the time,
scientists were constantly analyzing and improving their theoretical methods of creating one.
Now that it is becoming possible to actually create one, their hard work is paying off, drastically
reducing the previously astronomical cost a quantum computer would theoretically require
previously, both in terms of resources and finances.
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In 2010, scientists began working on ways to physically create a quantum computer, with
several possible ways to accomplish this. “The simplest system for investigating the interactions
between light and matter is a so-called cavity resonator with exactly one light particle and one
atom captured inside (cavity quantum electrodynamics, cavity QED). Yet since the interaction is
very weak, these experiments are very elaborate. A much stronger interaction can be obtained
with nano-structured circuits in which metals like aluminum become superconducting at
temperatures just above absolute zero (circuit QED). Properly configured, the billions of atoms
in the merely nanometer thick conductors behave like a single artificial atom and obey the laws
of quantum mechanics. In the simplest case, one obtains a system with two energy states, a socalled quantum bit or qubit. Coupling these kinds of systems with microwave resonators has
opened a rapidly growing new research domain in which the TUM Physics, the WMI and the
cluster of excellence Nanosystems Initiative Munich (NIM) are leading the field” (Agbenyega,
12).
Quantum computers are also beginning to be funded, in no small part due to their
incredible applications. “In September, Google recruited [John Martinis] and his 20-member
research team from the University of California, Santa Barbara, and set them to work on the
notoriously difficult task of building quantum computers: devices that exploit the quirks of the
quantum world to carry out calculations that ordinary computers could not finish in the lifetime
of the Universe… the quantum effects essential in such a computer are incredibly fragile and
hard to control: if one stray photon or vibration from the outside hits the device in the wrong
way, the calculation will collapse. Even today, after three decades of effort, the best quantum
computers in the world are barely able to do school-level problems such as finding the prime
factors of the number 21… But maybe not. Many physicists in the field think that their 30-year
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slog may finally be on the verge of paying dividends. Not only can they now generate quantum
bits, or 'qubits', that last for minutes instead of nanoseconds, they are also much better at
correcting the system when errors arise from outside perturbations and other causes. At the same
time, quantum-software engineers are coming up with applications that could justify the expense
of developing these machines, such as finding new catalysts for industrial processes” (Gibney).
Quantum computers have been a very difficult device to develop since their conception,
but their current state rests entirely on funding. Quantum computers have reached their
theoretical limit, and any future success or failure depends mainly on the physical work and
money invested into them. While unforeseen obstacles could still make quantum computers an
impossibility, it would be worth the investment to see how far we could develop them currently.
Google is also supporting scientists in Australia, who are presently attempting to create a
working, large scale quantum computer using silicon. “So far, the UNSW team has demonstrated
a system with quantum bits, or qubits, only in a single atom. Useful computations will require
linking qubits in multiple atoms. But the team’s silicon qubits hold their quantum state nearly a
million times longer than do systems made from superconducting circuits, a leading alternative,
UNSW physicist Guilherme Tosi told participants at the event. This helps the silicon qubits to
perform operations with one-sixth of the errors of superconducting circuits. If the team can pull
off this low error rate in a larger system, it would be “quite amazing”, said Hartmut Neven,
director of engineering at Google and a member of the panel. But he cautioned that in terms of
performance, the system is far behind others. The team is aiming for ten qubits in five years, but
both Google and IBM are already approaching this with superconducting systems. And in five
years, Google plans to have ramped up to hundreds of qubits” (Gibney, 448).
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Outlooks vary from person to person, complicating the issue further. While those
questioned in the article were very optimistic, scaling the quantum computer up might prove
impossible due to the increased chance of errors with the system. Quantum computers are almost
too hypothetical to take a concrete stance on, but there is currently enough evidence to lend
credibility to either viewpoint.
There is also another theory that supports the pessimistic theory: the “closed box theory”.
According to an article from Nature, “Perhaps the most critical, universal aspect of quantum
computers is the 'closed box' requirement: a quantum computer's internal operation, while under
the programmer's control, must otherwise be isolated from the rest of the Universe. Small
amounts of information leakage from the box can disturb the fragile quantum mechanical waves
on which the quantum computer depends, causing the quantum mechanically destructive process
known as decoherence” (Ladd et al, 45).
The closed box theory, if correct, would be the last nail in the quantum computer coffin.
If a quantum computer can only exist in an impossible vacuum (and cannot even exist in the
most physically possible vacuum available), then it would be impossible to actually create a
working one. There’s a possibility that the information leakage wouldn’t completely obstruct the
quantum computer’s processing. However, if the quantum computer is actually that delicate, or
even close to that delicate, it would be completely unfeasible to use one, dooming the entire
project to failure.
Furthermore, John Preskill notes that, even if quantum computers were developed in the
21st century, we have no idea what the technology would look like, or how we would handle
error correction, one of the biggest hurdles of quantum computers. John Preskill writes, “Many
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of us are hopeful that quantum computers will become practical and useful computing devices
some time during the 21st century. It is probably fair to say, though, that none of us can now
envision exactly what the hardware of that machine of the future will be like; surely, it will be
much different from the sort of hardware that experimental physicists are investigating these
days…As recently as mid-1995, we did not have a clear idea how quantum error calculation
would work, or whether it would work” (Preskill, 385).
While the article was written in 1998, and with quantum computers being possible (with
several prototypes already being created), Preskill’s point still stands. The development of
quantum computers is difficult to predict, and we still don’t know enough about the technology
or quantum mechanics to determine how feasible they are. At this time it feels like a coin toss,
with the discovery of a massive breakthrough or insurmountable obstacle being equally likely at
this point.
Kalai continues voicing his thoughts by analyzing the pessimistic hypothesis. “Under the
pessimistic hypothesis, universal quantum devices are unavailable, and we need to devise a
specific device in order to implement a specific quantum evolution. A sufficiently detailed
modeling of the device will lead to a familiar detailed Hamiltonian modeling of the quantum
process that also takes into account the environment and various forms of noise. Our goal is
different: we want to draw from the pessimistic hypothesis predictions on noisy quantum circuits
(and, at a later stage, on more general noisy quantum processes) that are common to all devices
implementing the circuit (process)” (Kalai, 514).
Kalai’s opinion is that, while quantum computers might not be feasible yet, or at all, due
to quantum noise, attempts to develop it will lead to an improved knowledge of quantum noise in
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general. By understanding and modeling the quantum noise itself, Kalai hopes that people will be
able to comprehend quantum noise as a whole. In the best case scenario, people would obtain a
sizeable amount of knowledge on quantum mechanics in general. This could lead to more
quantum machines in general, and possibly even quantum computers themselves.
My personal opinion is that, while I am not very knowledgeable on the subject, that
quantum computers are feasible and possible, it’s just a matter of time. While it seems unfeasible
and difficult to harness at the moment, quantum computers have too many possible applications
to ignore. Depending on the amount of manpower, money, and time invested in their
development, I would say that, barring unforeseeable or impossible to fix issues, quantum
computers may very well be developed within this decade. As simple as it sounds, large
corporations (and, more directly, money) are the biggest factor in developing quantum
computers. The more money that is invested in quantum computing, the sooner scientists can
encounter and overcome unforeseen hurdles, the sooner they can tweak and perfect their work,
and the sooner quantum computers can become a reality.
Quantum computers are an odd, hotly debated topic in the field of technology. Whether
they come to fruition or not remains to be seen, but if they were developed, their impact would
be massive. The topic is very divisive, with many top scientists split on whether it’s possible to
create one or not. While it is impossible to predict the development of quantum computers,
corporations seem to have taken an interest in it, increasing the possibility of seeing them in this
century, or even this decade. We will just have to wait and see.
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Works Cited Page
1. Majot, Andy and Yampolskiy, Roman. “Global catastrophic risk and security
implications of quantum computers”. Published Sept. 01 2015, Futures, Science Direct,
accessed Oct. 25 2016. Web.
2. Palma, G. Massimo, Kalle-Antti Suominen and Artur K. Ekert. “Quantum Computers and
Dissipation.” Published Mar. 8 1996, Proceedings: Mathematical, Physical and
Engineering Sciences, Royal Society, accessed Oct. 25 2016. Web.
3. Lanyon, B. P., Whitfield, J. D., Gillett G. G., Goggin, M. E., Almeida M. P. “Towards
quantum chemistry on a quantum computer”. Published Jan. 10 2010, Nature Chemistry,
ProQuest, accessed Oct. 25 2016. Web.
4. Kalai, Gil. “The Quantum Computer Puzzle”. Published May 1 2016, Notices of the
American Mathematical Society, American Mathematical Society Publications, accessed
Oct. 25 2016. Web.
5. O'Brien, Jeremy L. “Optical Quantum Computing.” Published Dec. 7 2007, Science,
JSTOR, accessed Oct. 25 2016. Web.
6. Agbenyega, Johnathan. “Quantum computers: Electronic Materials”. Published Sept.
2010, Materials Today, ScienceDirect, accessed Oct. 25 2016. Web.
7. Gibney, Elizabeth. “QUANTUM COMPUTER QUEST”. Published Dec. 4 2014, Nature,
ProQuest, accessed Oct. 25 2016. Web.
8. Gibney, Elizabeth. “Silicon quantum computers take shape in Australia”. Published May
24 2016, Nature, Nature, accessed Oct. 25 2016. Web.
9. T. D. Ladd, F. Jelezko, R. Laflamme, Y. Nakamura, C. Monroe, and J.L. O’Brien.
“Quantum computers”. Published Mar. 4 2010, Nature, Gale, accessed Oct. 25 2016.
Web.
10. John Preskill. “Reliable Quantum Computers”. Published Jan. 8 1998, Proceedings:
Mathematical, Physical and Engineering Sciences, Royal Society, accessed Oct. 25 2016.
Web.