The current state of quantum computing is referred to as the noisy intermediate-scale quantum (NISQ) era,
characterized by
quantum processors containing 50-100
qubits which are not yet advanced enough for
fault-tolerance or large enough to achieve
quantum supremacy
In quantum computing, quantum supremacy or quantum advantage is the goal of demonstrating that a programmable quantum device can solve a problem that no classical computer can solve in any feasible amount of time (irrespective of the usefulness of ...
.
These processors, which are sensitive to their environment (noisy) and prone to
quantum decoherence
Quantum decoherence is the loss of quantum coherence. In quantum mechanics, particles such as electrons are described by a wave function, a mathematical representation of the quantum state of a system; a probabilistic interpretation of the wave ...
, are not yet capable of continuous
quantum error correction
Quantum error correction (QEC) is used in quantum computing to protect quantum information from errors due to decoherence and other quantum noise. Quantum error correction is theorised as essential to achieve fault tolerant quantum computing that ...
. This intermediate-scale is defined by the
quantum volume
Quantum volume is a metric that measures the capabilities and error rates of a quantum computer. It expresses the maximum size of square quantum circuits that can be implemented successfully by the computer. The form of the circuits is independent ...
, which is based on the moderate number of qubits and
gate
A gate or gateway is a point of entry to or from a space enclosed by walls. The word derived from old Norse "gat" meaning road or path; But other terms include ''yett and port''. The concept originally referred to the gap or hole in the wall ...
fidelity. The term NISQ was coined by
John Preskill in 2018.
Algorithms
NISQ algorithms are designed for quantum processors in the NISQ era, such as the
variational quantum eigensolver (VQE) and
quantum approximate optimization algorithm (QAOA), which use NISQ devices but offload some calculations to classical processors.
These algorithms have been successful in
quantum chemistry
Quantum chemistry, also called molecular quantum mechanics, is a branch of physical chemistry focused on the application of quantum mechanics to chemical systems, particularly towards the quantum-mechanical calculation of electronic contributions ...
and have potential applications in various fields including physics, material science, data science, cryptography, biology, and finance.
However, they often require error mitigation techniques to produce accurate results.
Beyond-NISQ era
The creation of a computer with tens of thousands of qubits and enough error correction would eventually end the NISQ era.
These beyond NISQ devices would be able to, for example, implement
Shor's algorithm for very large numbers and break
RSA
RSA may refer to:
Organizations Academia and education
* Rabbinical Seminary of America, a yeshiva in New York City
*Regional Science Association International (formerly the Regional Science Association), a US-based learned society
*Renaissance S ...
encryption.
See also
*
Quantum supremacy
In quantum computing, quantum supremacy or quantum advantage is the goal of demonstrating that a programmable quantum device can solve a problem that no classical computer can solve in any feasible amount of time (irrespective of the usefulness of ...
References
External links
John Preskill lecture on NISQ era
{{History of physics
Computer architecture statements
History of computing hardware
Quantum computing
Quantum information science
Computational complexity theory