glossary

Key Terms

• Qubit: A quantum bit, the basic unit of information in a quantum computer. Unlike classical bits that can be 0 or 1, a qubit can also exist in a superposition of both states simultaneously.
• Superposition: A fundamental principle of quantum mechanics where a quantum system can exist in multiple states at the same time until it is measured.
• Entanglement: Another quantum phenomenon where two or more qubits become linked together in such a way that they share the same fate, no matter how far apart they are. Measuring the state of one entangled qubit instantly influences the state of the others.
• Quantum Algorithm: A computational procedure designed to run on a quantum computer, leveraging quantum phenomena like superposition and entanglement to solve certain problems more efficiently than classical algorithms.
• Quantum Supremacy (or Quantum Advantage): The point at which a quantum computer can solve a problem that no classical computer can solve in a feasible amount of time.
• Quantum Error Correction: Techniques used to protect quantum information from errors caused by noise and decoherence, which are significant challenges in building stable and scalable quantum computers.
• Surface Code: A specific type of quantum error-correcting code that is considered a leading candidate for building fault-tolerant quantum computers.
• Topological Qubit: A type of qubit that is theoretically more resistant to local noise due to its quantum state being encoded in the topology of the system. Microsoft is a major proponent of this approach.
• NISQ (Noisy Intermediate-Scale Quantum): The current era of quantum computing characterized by quantum computers with a limited number of qubits and high error rates, making it challenging to run complex algorithms.
• Decoherence: The loss of quantum coherence, where a qubit in a superposition collapses to a definite classical state due to interaction with its environment.
• Cryogenic: Relating to very low temperatures. Many current quantum computing platforms require extremely cold operating temperatures (close to absolute zero) to maintain qubit coherence.
• Photonic Quantum Computing: A type of quantum computing that uses photons (particles of light) to encode and manipulate quantum information. PsiQuantum utilizes this approach.
• Logical Qubit: A fault-tolerant qubit created by encoding quantum information across multiple physical qubits and using error correction to reduce the overall error rate.
• Physical Qubit: The fundamental hardware component that aims to represent a qubit, but is subject to noise and errors.
• Quantum Gate: An elementary operation performed on qubits, analogous to logic gates in classical computing, used to manipulate the quantum state of qubits.