Skip to content

NISQ Devices — Are They Quantum Computers or Not Quite Yet?


Mar 20, 2023 - 6 minute read

3036 Blog Post NISQ Devices 416X300
Michał Bączyk Quantum Computing Specialist

He is a Cambridge and ETH Zurich graduate. Over the course of his career, Michał completed internships in Quantum AI groups at CERN and Los Alamos National Laboratory in the United States. In his work, he aims to connect the worlds of quantum computing and business.

See all Michał's posts

2988 HC Digital Transformation 476X381


The term NISQ is relatively new, coined in 2018 by Caltech Professor John Preskill. It refers to the era of noisy intermediate-scale quantum computing that we are experiencing, and is characterised by the current state of quantum hardware processors. For now, these processors are referred to as NISQ devices since they don’t possess all the capabilities of a fully functional quantum computer. A noisy intermediate scale quantum (NISQ) device is a quantum computer that is not as powerful as it would need to be to solve the hard problems in quantum computing, but it still has enough capabilities to be useful for solving less complex problems.

The year 2019 was very memorable for quantum computing enthusiasts. This is when we all heard the world celebrating quantum supremacy. Google announced they managed to solve a computational task that would take the most powerful classical supercomputer 10000 years to complete in just 200 seconds. They achieved it with a 54 qubits chip called Sycamore. It was the revolutionary moment when we started to realise that quantum revolution is on its way, and when it arrives, it will be a massive leap in technological progress.

The claims caused not only a lot of excitement but also disbelief in the soundness of the results. The scientific community still investigates the exact details of those claims and, in 2022, a paper was published that it might be possible to beat Sycamore. All these discussions pose one serious yet simple question: do we already have a quantum computer?

Therefore, I decided to give a detailed overview of the current state of play, as well as explain a few technical details to provide you with a more concrete understanding of what they mean.

Quantum Computers and NISQ Devices: What's the Difference?

The goal of both quantum computers and NISQ devices is to execute quantum algorithms. A quantum algorithm is a set of instructions given to a quantum computer. It can be seen as a series of steps that convert a quantum system from one quantum state to another.

The operations of a quantum processor are vastly different from those of a classical computer. In classical computing, each operation is a mathematical transformation that is set in stone. However, for quantum processors, such certainty and definiteness is yet to be achieved.

Quantum processors work with qubits, which are represented by single physical objects, while bits are represented by around one million physical objects, providing an excessive amount of redundancy. As a result, processing quantum information is a much more challenging task.

Each operation is susceptible to noise that can spread throughout an entire quantum registry, potentially causing significant information to be lost and the output to appear random. In addition, each qubit can only be stored for a limited time because it deteriorates. All these factors determine the quality of a quantum processor.

NISQ devices are the first working models of quantum computers, however, they cannot yet operate with an adequate level of efficiency. They hold great promise for the future of computing and can be useful for prototyping subsequent quantum computers. By understanding and observing the behaviour of these devices, we can learn how to build larger, operational quantum computers in the future.

Quantum Computers: Why Can't We Build Them Today?

The goal is to build a fault-tolerant quantum computer. That means a processor that would be able to operate properly and with maintained efficiency and quality of calculations, even if some of its components occasionally fail. Such a fault-tolerant computer with proper size would be able to achieve quantum supremacy that wouldn’t be disputable.

There are at least a few challenges to overcome in order to unlock the potential of fully operational quantum computers.

  1. To overcome the decoherence process that qubits are prone to. Decoherence causes the definiteness and quality of information to degrade with time even if no quantum operations are applied and the information is just stored in the quantum registry.
  2. To construct gates with adequate fidelity, i.e., to assemble quantum operations between qubits that don’t generate significant amounts of errors. Moreover, the gates must form a universal set of gates, which means that any arbitrary operation might be constructed from them. Hence, not only the simplest operation must be implemented but also ones with the capability to generalise their effect to any transformation.
  3. To establish logical qubits. They’re collections of qubits that, although individually prone to error, together can constitute a well-defined unit of quantum information. The process of eliminating single qubit errors to build logical qubits is called quantum error correction.
  4. To measure in a reliable way. At the end of each calculation comes the measurement process, which provides the results of quantum computation. If the measurement process is not adequate, it might negatively affect the distributions of the results, causing them to not reflect the actual output.
  5. To scale. If we achieve 5 logical fault-tolerant qubits but don’t know how to use a similar approach to construct significantly larger devices, there will be no significant difference to computations performed nowadays.

Can My Business Benefit From the NISQ Technology?

Though we have not yet mastered building flawless quantum processors, NISQ devices already are a tremendous technological advancement that can bring value to your business. They employ the laws of quantum physics to their advantage, what makes the way they operate vastly different from classical computers.

There are four advantages that distinguish quantum as a computational framework.

What is the Future of the NISQ Devices?

Although the errors present in current quantum processors will still be a part of each execution of quantum algorithms, NISQ devices will deliver business value in the near future. That is because there are ways to make these errors negligible for specific purposes.

First, research and advances in qubit processing have led to more stable qubits and qubit gates, meaning that operations can be performed with more fidelity. We’re also making headway in terms qubits being operated with tighter coherence, as well as in possibilities of correcting the quantum states. The rate of improvement is encouraging.

The second step is to employ error mitigation techniques. There are some general methods and implementations, but they are working the best when they’re tailored to the algorithm and hardware. In other words, these methods are most successful when they consider the limitations of the quantum processing units and the model that will be used in your computations.

In error mitigation, the output of the quantum hardware is observed for specific operations on intentionally selected qubits. For simple cases, you’ll know the desired output, and you’ll be able to use it as a benchmark against the produced values. Such a procedure gives insights on the noise that’s introduced by specific operations using specific gates. Taking that into account, the discrepancies in performance between a NISQ device and an ideal machine might be reduced, allowing us to achieve approximate error suppression.


The first quantum computers are almost ready for use. They ‘e called Noisy Intermediate Scale Quantum (NISQ) computers and they’re the first steps toward full-scale quantum computing. NISQ devices are built on the same principles as quantum computers, but do not have the same capabilities.

In this article, I outlined the crucial limitations of NISQ devices. Even in their current state, however, they have immense potential and can be used to gain insights that were previously out of reach. If you’re interested in learning about the current status of quantum technology and whether it might be a good fit for you today, don’t hesitate to check our quantum computing services page or reach out to us directly. We stay up to date on all new advancements and are ready to guide you through this ever-evolving world.

2988 HC Digital Transformation 476X381
Michał Bączyk Quantum Computing Specialist

He is a Cambridge and ETH Zurich graduate. Over the course of his career, Michał completed internships in Quantum AI groups at CERN and Los Alamos National Laboratory in the United States. In his work, he aims to connect the worlds of quantum computing and business.

See all Michał's posts

Related posts

You might be also interested in


Start your project with Objectivity

CTA Pattern - Contact - Middle

We use necessary cookies for the functionality of our website, as well as optional cookies for analytic, performance and/or marketing purposes. Collecting and reporting information via optional cookies helps us improve our website and reach out to you with information regarding our organisaton or offer. To read more or decline the use of some cookies please see our Cookie Settings.