The field of quantum computing is incredibly exciting and in equal parts, terrifyingly complex – at least for your humble author. Without diving too far into the rabbit hole, this article seeks to answer some of the basic questions; What is the current landscape? Is anybody using Quantum Computing and what does the future hold?
To answer these questions we spoke with Michel Kurek.
What is a quantum computer?
Similar to the computers we know, Quantum Computers can store, process and read information. This is where the similarities end. Information in Classical computers (yes they do call them classical now) is stored in binary digits of 1’s and 0’s. In Quantum Computing, information is stored in Qubits.
What is a Qubit and why is it important?
Qubits are typically the information unit coded in atomic or subatomic particles. With a spot of clever engineering, Quantum computers can manipulate a Qubit into a superposition or entangle two qubits to create a quantum correlation effect. In superposition, a Qubit can represent numerous combinations of 1’s and 0’s at the same time. This means the Quantum Computer can perform simultaneous computations on the same Qubit, dramatically increasing its computational ability.
Or in more technical terms, Superposition allows a qubit to encode several pieces of information in parallel. The state of the qubit is a linear combination of the states 0 and 1 (in a proportion defined by two numbers). It is the superposition of the encoded states that provides the power of representation and processing of the quantum information. A register of 2 qubits makes it possible to represent or process the equivalent of 4 bits, 3 qubits the equivalent of 8 bits, and n qubits the equivalent of 2n bits. Adding a qubit to a quantum register doubles the power of the system. And 64 qubits? They give you 2^64, which is 18,446,744,073,709,600,000! That’s about one million terabytes in classical computing.
In quantum computing, entanglement allows the implementation of powerful logical operators/gates that can make the computation even more efficient.
An industry standard for Quantum Computing is still to be determined so when discussing Quantum Computers, we are really discussing Qubits and Quantum Gates. There are currently 6-7 different types of qubits (see fig.1) being applied in industry and each have their own engineering challenges.
Fig.1 Source. Michel Kurek, Feb 2021.
Depending on the application, different Qubits can be used for different problems. For example, Photons are the only Qubit that can travel and can be maintained at room temperature which makes them a prime candidate for quantum communication.
Within Quantum Computing, the approach taken by most of the IT giants (excluding Microsoft) uses the superconducting properties of electrons. This requires cryogenic freezing of the electron to around 15 milli-Kelvin (slightly colder than a January morning in Chicago).
Another approach uses ions. This involves trapping an ion particle within a vacuum and is being driven by companies like IONQ and also the conglomerate, Honeywell.
In order to process the Qubits, as in classical computing, a quantum circuit applies gates (using for example microwaves or lasers) to manipulate the quantum information and finally compute an answer. There is one other way, called Quantum Annealing which is used by D-Wave (one of the industry leaders). Quantum annealing is a metaheuristic for finding the global minimum of a given objective function over a given set of candidate solutions (candidate states), by a process using quantum fluctuations. It works well on very specific problems like optimisation and if you were interested you can pick up a Quantum Annealing computer from D-wave for between $10-15ml.
Problems with Quantum Computing
There are many. The biggest one is fault tolerance. Qubits are incredibly hard to maintain. Even the slightest bit of noise (background radiation, electromagnetism, a large sneeze) impacts the Qubit making it irrelevant. The current understanding is that 1,000,000 Qubits would only really 