Quantum Computing
What is Quantum Computing?
A subfield of quantum information science, quantum computing is the performance of computation via the exploitation of the properties of quantum states. While uncertainty is unacceptable in classical computing, uncertainty is an asset in quantum computing. Through dealing with complex algorithms and probability, quantum computers are able to generate multiple answers leading to the generation of complex decisions.
History
The history of quantum computing dates back to 1980 when physicist Paul Benioff proposed the quantum mechanical model of the Turing machine. Physicists such as Richard Feynman and Yuri Manin hypothesized that quantum computers had the potential of being able to simulate and perform actions that were not feasible even by the most powerful supercomputers.
Interest and excitement about quantum computing was stimulated in 1994 when Peter Shor debuted a quantum algorithm that could factor large prime numbers faster and more efficiently than any classical algorithm. Through the 1990s and early 2000s, however, the development of a physical quantum computer was still seen as a distant dream due to many obstacles. However, on October 23, 2019, Google AI in partnership with NASA claimed to have performed a quantum computation. Quantum computers today have the capacity to make use of less than 20 qubits. IBM, Google, and Microsoft are among the companies that are trying to make larger scale quantum computing systems that are stable.
How Does It Work?
Although there are several types of quantum computing systems, the most prolific model is the quantum circuit. This model makes use of the basic properties of quantum computing: superposition and entanglement. These two properties together allow for a system with the potential ability to perform many operations simultaneously.
Superposition
Superposition is the ability of a quantum system to exist in multiple states simultaneously. Whereas classical computing is based on bits, which have a value of either 0 or 1, quantum computing is based on quantum bits, referred to as “qubits,” which can hold a combination of 0 and 1 simultaneously, 0 only, 1 only, and the infinite number of values between 0 and 1. This behavior is only observed at an atomic level. Once the qubit is measured, it has the value of either 0 or 1. This can be visualized in the example of a coin toss. Possible results of a coin flip are 1. heads and 2. tails. However, when the coin is in the air, it is heads and tails at the same time. Upon landing (analogous to the measurement of a qubit), however, the coin toss will have the value of heads or tails. Quantum computers can also create complex superpositions of 0 and 1 upon interaction with other qubits. The total number of superpositions is calculated as 2^n where n is the number of qubits. Interference is a byproduct of superposition, as it is used to control quantum states and amplify signals that lead to the right solution based on probability while simultaneously canceling the signals leading to the wrong solution. This contributes to the overall efficiency of the system as it creates bias toward the desired solution or state.
Entanglement
Quantum entanglement is the extremely strong correlation existing between qubits even when separated by a great distance. The state of one qubit(qubit A) that is entangled with another qubit (qubit B) cannot be described separately from the state of qubit B. Therefore, when you measure qubit A, you also get some information about what would happen if you measure qubit B. This leads to higher efficiency of the system, allowing a solution to be reached faster and also with fewer calculations.
It must be noted that quantum computers are not a replacement for classical computing, as there are only a few problems that a quantum system can perform with tremendous speed compared to classical computing systems. These problems include the factorization of a large number and the determination of the bond length on chemical compounds.
Obstacles
- Developing the technology to keep the system stable as the number of qubits increases.
- Quantum computing incorporates concepts from highly complex fields that are not fully developed such as quantum physics, superconductors, and nanotechnology.
- Quantum systems, in order to not undergo decoherence (the gradual loss of the quantum state), must operate in isolation from the outside environment. However, in order to perform an quantum operation, interactions such as measurement or manipulation of the state of qubits is necessary to get any data output. Minimizing and preventing decoherence is, then, a major obstacle in the field of quantum computing.
Applications
Quantum computing has many applications and has the potential to aid in the advancement of many fields including chemistry, materials science, nuclear physics, and machine learning. The following applications will potentially benefit from advances in quantum computing:
- Machine Learning
- Super-Catalyst Design
- Medicine
- Chemistry
- Climate Change/Earth Science
- Battery Chemistry
- Material Science
- Engineering
- Artificial Intelligence
- Information Security
- Biomimetics
- Energy
- Photovoltaics
- Financial Services
- Supply Chain & Logistics
How to Get Started
First, computer engineers should become familiar with quantum computing fundamentals such as superposition and entanglement as discussed above. Access to quantum computers is available globally through a few open source systems. IBM’s IBM Q Experience and the open source Qiskit platform allows access to real quantum hardware, and 100 million experiments have been performed through this platform by 145,000 users. De-Wave Systems, Inc. and Rigetti Computing, and Google also offer free resources to interact with quantum computing systems and simulations. Rigetti Computing currently has a 128-qubit model, and currently through QCS offers access to a 16-qubit chip. Google has a 72-qubit Bristlecome chip. According to Hartmut Neven, director of the Quantum Artificial Intelligence lab at Google, “quantum computers are gaining computational power relative to classical ones at a ‘doubly exponential’ rate.”
Conclusion
Although there have been many relevant quantum computing experiments performed, a truly relevant and stable quantum computing machine is likely decades away from production.