Canada’s charming and handsome Prime Minister was asked a question by reporter on Quantum Computing. What is Quantum Computing, he asked. And then, as if to suggest the question was far above the intelligence of the Canadian Prime Minister, went to ask him about Canada’s response to Islamic State. The intention of the reporter was clear – that this young PM was basically inexperienced and lacking in knowledge on things he was trying to promote. What happened then was remarkable. Justin Trudeau then schooled the guy in Quantum Computing before he went on to reply the question on IS.

Justin Trudeau and What is #Quantum Computing? #Trudeaumania Click To TweetHere is the video.

Let us now understand what Quantum Computing really is. It is based on the understanding of Quantum Physics and the related concepts like Quantum Entanglement, Superimposition and Quantum Tunnelling. To get a quick primer on Quantum Mechanics, here is an interesting documentary.

## Origin of Quantum Computing

Paul Benioff first applied the quantum theory to computers in 1981 and theorized about the Quantum Turing Machine. He worked at the Argonne National Laboratory.

The major contributors in the field of Quantum Computing have been – Yuri Manin, Richard Feynman and David Deutsch .

## What are Qubits?

The basis of Quantum Computing lies in the research on Quantum Physics, where an electron can be in wave and particle state at the same time, depending on the act of observation. So when you measure the spin of qubits, they can be in the “up” or “down” states, but before that they could be in both the states!

Unlike analog computers, as the PM Justin Trudeau correctly asserted, where the information is stored and used as binary bits (0 or 1), in Quantum Computers, Qubit is used as the unit of information. Here is a quick comparison of Qubits and Analog bits.

## Qubits vs Analog bits

The classical or analog bits – 0 or 1 state – allow the programmers to use just two states and **either of the four combinations** – 0-1, 0-0, 1-1, 1-0 – to create their codes. In case of Quantum Computing however, one can **superimpose all the four states** of spin of quantum or Qubits – Up-Up, Up-Down, Down-Down, Down-Up –** at the same time**!

**How does a Quantum Computer Work?**

Here is an excellent video on a brief, simple but well-articulated lesson on how a Quantum Computer works?

## Quantum Computation Paradigms: Gate Model and Quantum Annealing

The power of Quantum Computing comes from using the Quantum Superimposition (both states at the same time), and combining it with Quantum Entanglement and Quantum Tunnelling to use and manipulate all combinations of the bits simultaneously!

This enables a Quantum-based processor to solve much more complex problems in a remarkably short time.

There are two paradigms of Quantum Computation: **The Gate Model** and **Quantum Annealing** (Quantum Adiabatic Computation).

**Quantum Gates Model:** Uses the Quantum gates which are basic quantum circuits using small number of qubits.

Unlike many classical logic gates, quantum logic gates are reversible. However, it is possible to perform classical computing using only reversible gates. For example, the reversible Toffoli gate can implement all Boolean functions. This gate has a direct quantum equivalent, showing that quantum circuits can perform all operations performed by classical circuits.

Quantum logic gates are represented by unitary matrices. The most common quantum gates operate on spaces of one or two qubits, just like the common classical logic gates operate on one or two bits. This means that as matrices, quantum gates can be described by 2 × 2 or 4 × 4 unitary matrices.

In a remarkable breakthrough, a team of engineers at University of New South Wales used the quantum gates paradigm to develop a device that allowed two quantum bits to effectively communicate with each other. Using silicon, along with this theoretical paradigm, a practical quantum computer could be possible!

**Quantum Annealing:** Many research efforts in this direction are using Quantum Annealing to solve these complex problems. It is a paradigm of Quantum Computation.

Annealing uses “tunes” the many states of qubits – including their superimposed state – to a classical state and solve for the best solution. In fact D-Wave systems, a Canadian company, has developed a hardware to use this concept of Quantum Annealing to create a Quantum Computer. Their customers include Google, NASA, Lockheed-Martin.

Quantum annealing is a computational paradigm to search for the minimum of a cost function (multivariable function to be minimized) through a control of quantum fluctuations. Quantum annealing is used mainly for combinatorial optimization problems with discrete variables. (Source)

Here is a very useful talk on “Theory of Quantum Annealing” by Hidetoshi Nishimori at Google in 2014.

## Future of Quantum Computing

Even though the promise and power of quantum computing is tremendous, the progress in pure quantum computing is slow and painful.

Therefore, as per most estimates the short term work will be in the hybrid models – as the work of D-Wave systems suggests. The greatest challenge is how to manage the incredible power and speed of quantum computing with the possibility of the exponential complexity needed to handle such a system!

When asked to articulate the tremendous complexity in creating the right Quantum Computer, Ivan H Deutsch – a pioneer who is working to create a quantum computer – said:

The hardware problem is that the superposition is so fragile that the random interaction of a single qubit with the molecules composing its immediate surroundings can cause the entire network of entangled qubits to delink or collapse. The ongoing calculation is destroyed as each qubit transforms into a digitized classical bit holding a single value: 0 or 1.

To circumvent the complexity, Ivan Deutsch and his team have been trying to use a “qudit”. Qudit is a complete atom as opposed to a fundamental particle or an electron which is the basis of Quantum Physics. It works “*in a sort of fake or simulated quantum superposition in which it’s allowed to occupy one of 16 different states, represented by energy levels”.* This helps in managing the complexity, while getting tremendous enhancements in speed and computing power.

So folks, the future of computing is coming. Albeit slowly.

Featured Image: Pixabay

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