Quantum Computing
A simple introduction to Quantum Computing
1. Why should we even build a quantum computer?
Even the most powerful supercomputers on earth don’t have enough computational power to solve some problems above a certain size and complexity. For example, some processes in nature are impossible to simulate on a classical machine due to the tremendous number of different configurations and possible states of the system. Quantum computers are pushing the boundaries of computation, and in the next decades, the community is expecting a number of major breakthroughs in many fields.
2. Basic idea of quantum computing
It’s a new kind of computing that harnesses quantum mechanics phenomena by controlling the behavior of fundamental particles. While classical computers work their magic by using individual bits that can be set to either 0 or 1, a quantum computer employs artificial atoms called qubits that are non-binary and exist on a spectrum of different values from 0 to 1, and can even be in two states at the same time, which brings us to our next point.
3. A little bit of physics
A few quantum properties are used to manipulate the state of a qubit:
Superposition: it’s basically the idea that a quantum particle can be in a combination of different states. You’re probably familiar with Schrödinger’s thought experiment which states that a cat is both dead and alive before actually observing it.
Entanglement: a very weird and counter-intuitive phenomenon that refers to the behavior of entangled particles as if they were connected by what Einstein called “Spooky action at a distance”.
Interference: very much like regular wave interference, except that the waves in quantum physics are related to probability.
4. Potential applications:
Artificial intelligence: machine learning, self-driving cars, algorithms that will help diagnose illnesses, quantum computing will spur the development of AI as well as medicine.
Healthcare and medicine: the design and modeling of molecules for drug development. Since quantum computers operate using the same properties as the molecule it’s trying to simulate, this could lead to treatments for diseases like Alzheimer’s.
Cryptography: quantum uncertainty can be leveraged to encrypt messages and transactions with unbreakable private keys.
The teleportation of information: it is possible thanks to entanglement.
Scientists also designed and implemented some interesting new protocols such as: teleportation among different users in a simulated network, efficient data transmission, and even secure voting.
5. Quantum programming:
There are several computing models, but the main one that’s largely physically implemented is the Quantum Gate Array (based on quantum circuits that are created and manipulated using Python, Swift or Java). But how can we actually use these computers you might ask? Well, there are many quantum software development kits that help you create and use algorithms and simulations through cloud-based quantum devices. You can get free access to it on the IBM website for example and experiment with Qiskit (an Open Source framework that you can use with Python).
6. Quantum Algorithms:
Let’s take a closer look at how a quantum algorithm actually works. Consider an optimization project where you have to find the best configuration of a number “n” of parameters. A classical computer would consider each possible configuration individually and then compare them all. A quantum computer would solve it as follows:
1. Activate the spread: putting the qubits in a superposition of all “2n” states.
2. Encode the problem: the problem is encoded onto the system by applying gates. We set the phase and amplitude and other parameters.
3. Solve the problem: using the principle of interference to magnify the amplitude of the correct answer and shrink the wrong ones. Some iteration might be needed.
