# noisy intermediate-scale quantum era

> era of technology characterized by quantum processors with <1000 qubits sensitive to noise, prone to quantum decoherence, and incapable of continuous quantum error correction

**Wikidata**: [Q97323823](https://www.wikidata.org/wiki/Q97323823)  
**Wikipedia**: [English](https://en.wikipedia.org/wiki/Noisy_intermediate-scale_quantum_computing)  
**Source**: https://4ort.xyz/entity/noisy-intermediate-scale-quantum-era

## Summary
The noisy intermediate-scale quantum era (NISQ) is a period in quantum computing characterized by quantum processors with fewer than 1000 qubits that are highly sensitive to noise and prone to quantum decoherence. These devices cannot yet perform continuous quantum error correction, limiting their reliability and scalability. This era represents the current state of quantum technology before fault-tolerant quantum computers become available.

## Key Facts
- NISQ stands for "Noisy Intermediate-Scale Quantum" era
- Quantum processors in this era have fewer than 1000 qubits
- Devices are highly sensitive to environmental noise
- Quantum decoherence is a major challenge during this era
- Continuous quantum error correction is not yet feasible
- The term was coined by John Preskill in 2018
- This era bridges the gap between current quantum devices and future fault-tolerant quantum computers
- NISQ devices are used for quantum simulation and optimization problems
- The era is part of the broader field of quantum information science
- Multiple language Wikipedia pages exist for this topic (ca, de, en, es, fr, it, uk, zh)

### Q: What is the noisy intermediate-scale quantum era?
A: The noisy intermediate-scale quantum era (NISQ) is a period in quantum computing where quantum processors have fewer than 1000 qubits and are highly sensitive to noise and decoherence. These devices cannot yet perform continuous quantum error correction, limiting their capabilities.

### Q: Who coined the term NISQ?
A: John Preskill coined the term "Noisy Intermediate-Scale Quantum" (NISQ) in 2018 to describe the current state of quantum computing technology.

### Q: What are the limitations of NISQ devices?
A: NISQ devices are limited by their sensitivity to noise, susceptibility to quantum decoherence, and inability to perform continuous quantum error correction. These limitations restrict their reliability and scalability for complex computations.

### Q: How many qubits do NISQ devices typically have?
A: NISQ devices typically have fewer than 1000 qubits, placing them in the "intermediate-scale" category of quantum processors.

### Q: What comes after the NISQ era?
A: After the NISQ era, the field aims to develop fault-tolerant quantum computers that can perform continuous quantum error correction and scale to thousands or millions of qubits reliably.

## Why It Matters
The noisy intermediate-scale quantum era represents a critical transitional phase in quantum computing development. It matters because it defines the current technological landscape where quantum computers exist but have significant limitations. This era is crucial for developing practical applications of quantum computing while researchers work toward more robust, error-corrected systems. NISQ devices are already being used for quantum simulation, optimization problems, and exploring quantum algorithms, providing valuable insights into quantum computing's potential. The challenges faced during this era—noise sensitivity, decoherence, and error correction—are driving innovation in quantum hardware and software. Understanding NISQ is essential for researchers, investors, and businesses looking to engage with quantum computing technology today, as it sets realistic expectations for what current quantum devices can achieve while highlighting the path forward to more powerful quantum systems.

## Notable For
- Being the current state of quantum computing technology
- Defining the limitations and capabilities of near-term quantum devices
- Coined by prominent physicist John Preskill in 2018
- Bridging the gap between current quantum devices and future fault-tolerant systems
- Enabling practical quantum applications despite technological constraints

## Body
### Origins and Definition
The noisy intermediate-scale quantum era was formally defined by Caltech physicist John Preskill in a 2018 paper. Preskill introduced the term to describe the current state of quantum computing where devices exist but face significant technical challenges. The "noisy" aspect refers to the high error rates and sensitivity to environmental interference, while "intermediate-scale" indicates qubit counts below 1000.

### Technical Characteristics
NISQ devices operate with fundamental limitations that distinguish them from future fault-tolerant quantum computers. The noise sensitivity means that quantum states degrade rapidly due to interactions with the environment. Quantum decoherence causes quantum information to be lost over time, limiting computation duration. Without continuous quantum error correction, which requires substantial qubit overhead, these devices cannot maintain quantum states reliably for extended periods.

### Applications and Research
Despite limitations, NISQ devices are being used for various applications including quantum chemistry simulations, optimization problems, and machine learning tasks. Researchers are developing NISQ-era algorithms specifically designed to work within these constraints, such as variational quantum eigensolvers (VQE) and quantum approximate optimization algorithms (QAOA). These applications provide valuable experience with quantum computing while the technology matures.

### Industry Impact
The NISQ era has significant implications for quantum computing development timelines and investment strategies. Companies and research institutions are focusing on maximizing the utility of current devices while preparing for the transition to fault-tolerant systems. This period allows for the development of quantum software, algorithms, and expertise that will be essential when more capable quantum computers become available.