Tanisha Bassan


A Brief Introduction to Quantum Computing

Quantum physics to me was always this mystifying property which give unreal capabilities to subatomic particles. It was never anything more than just a great conversation starter I used to blow people’s minds away.

I mean come on, teleportation? Being in two place at once? Seems science fiction to me.

Now if you aren’t aware of quantum mechanics, basically electrons or any other subatomic particle have some wacky but neat super powers such as superposition, (the power to be a wave and a particle, at the same time) quantum tunnelling, (the power to bypass any barriers i.e move through walls) entanglement (the power to be psychic, like having a twin where if one is affected then simultaneously so is the other).

Neat, huh? Unfortunately us humans don’t have these super powers so these forces never really affect us or matter in the classical physics world.

Or so I thought.

Introducing: Quantum Computing

With quantum computing we can harness the super powers superposition and entanglement to solve complex problems that our classical computers cannot do. Thus a quantum computer uses the quantum phenomena of subatomic particles to compute complex mathematical problems.

A quantum computer uses qubits to supply information and communicate through the system. Its encoded with quantum information in both states of 0 and 1 instead of classical bits which can only be 0 or 1. This means a qubit can be in multiple places at once due to superposition.

Imagine the following example, I write an X on a random page in a random book in a library with 1 million books and tell a quantum and classical computer to find the X. For a classical computer, it would have to sort through every page of every book one by one to find the X which would consume a lot of time. For a quantum computer, a qubit in superposition can be in a multiple places at once so it can analyze every page at the same time and find the X instantly.

Superposition and entanglement in a quantum computer:

  • qubits unlike classical computers can be in a superposition of both 0 and 1
  • a complex system of qubits can be in many superpositions at once, example 5 qubits can be in a superposition of 32 states (2^n)
  • 2 entangled qubits are correlated with one another, information on one qubit will reveal information about the other unknown qubit
At about 50 qubits, many say a quantum computer could achieve “quantum supremacy” ~ John Preskill

Together both properties of superposition and entanglement will enable qubits to compute huge amounts of data simultaneously and solve complex problems such as optimization which classical computers would take millions of years to calculate.

Why is the optimization problem important?

An optimization problem is essentially finding the best solution to a problem from endless number of possibilities.

Classical computers would have to configure and sort through every possible solution one at a time, on a large scale problem this could take millions of years.

Quantum computers can find all possible variants at the same time using superposition and entanglement and sift through large amounts of data in a significantly small amount of time.

One problem we have now is simulating possible chemical compositions of different compounds due to complex structures that involve a lot of combinations of electron repulsion and attraction. It is another type of optimization problem with countless possibilities for bonds and shapes of molecules.

With quantum computing this problem is easily scalable with enough qubits to configure all possibilities for the structure of a molecule. It can be revolutionary for drug discovery in the pharmaceutical industry for classification of millions of drugs and optimizing for the best possible ones for a certain disease. This can be a game changer for personalized medicine, genomics, and being able to fully scale our DNA.

One company using this cutting edge technology is Biogen with Accenture labs and 1QBit to completely change the way of traditional drug discovery.

The process of computing on a quantum computer is very different from a classical computer. To solve optimization problems there are set algorithms used and qubits function a lot differently to reach the optimal value. The process is explained below in a very simple manner but in reality it is a lot more complex.

The Process of Utilizing Quantum Algorithms:

  1. Activate qubits to reach a superpositions of all possible states
  2. Encode the optimization problem by applying a phase on each superposition state
  3. Use methods of interference to cancel or add phases to optimize for the correct answer and shrink the wrong answers (like noise canceling in headphones)

However its not very easy getting qubits to cooperate with a system. As more number of qubits are added to a system the higher the error rates. To have a working computational quantum computer your system must satisfy these properties:

  • intialize all of your qubits to a known state
  • rotate individual qubits.
  • measure individual qubits.
  • perform an operation that entangles pairs of qubits.
  • stay free of outside interference (decoherence) for as long as it takes to finish a computation.

For a quantum computer to be functional it must have qubits that can harness quantum properties and have all possible measures must be taken to reduce error rates. Qubits are prone to instability and error which is why the system needs to be cooled down as close to 0 kelvin degrees and all accounts of error must be calculated to have a decoherent environment.

These are the types of qubits being used today:

The Canadian based quantum computer company D-Wave Systems Inc. has a 2000 qubit quantum computer on the market for $15 million. Pretty decent price I would say for a machine that can do math on just a couple atoms. It uses superconducting loops to create functional qubits. The other possible methods are being explored by large tech companies like Google, IBM, Intel, Microsoft, etc. Everyone is in the race to reach “quantum supremacy.” This is the point where quantum computers will outperform classical supercomputers. 2018 is another year for many future breakthroughs in quantum computers, there is no way to tell how soon we will reach quantum supremacy.

Why should we be excited about quantum computers?

Quantum computers are in their early stage of development much like the classical computers back in the 50’s. No doubt with the classical computers came revolutionary technology such as the internet so imagine the applications of quantum computers for the future. Who back in the 50’s could predict such a thing as social media and the concept of being connected to millions of people through transmitting signals?

Future Applications of quantum computers:

  • Better online security with development in quantum encryption
  • Significantly improve AI technology
  • Drug research and discovery
  • More accurate weather predictions
  • Optimizing traffic control

Key Takeaways:

  1. Quantum mechanics are the laws of subatomic particles with phenomenas such as quantum tunnelling, superposition and entanglement.
  2. Quantum computers will use qubits to encode quantum information and calculate complex mathematical problems using superposition and entanglement.
  3. Quantum computers can solve optimization problems which can revolutionize drug discovery and many more industries.
  4. Qubits are unstable and very susceptible to environmental changes, only work with 0 outside interference due to fragile system
  5. Many types of qubits being used today to create the world’s best functional quantum computer
  6. Lots of research still needed to create a quantum computer that can defeat our classical supercomputers

Stay tuned for more articles as I explain some of the more complex theories and types of qubits in quantum computing.

Comment below for more resources and information on quantum computing.

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