Quantum Computing vs Quantum Simulators vs Quantum Emulators

Quantum Computing vs Quantum Simulators vs Quantum Emulators – What’s The Difference?

Quantum computing is an exciting and rapidly advancing field that leverages the strange properties of quantum mechanics to perform computations in powerful new ways. However, there are several related terms like “quantum simulators” and “quantum emulators” that can cause confusion about what quantum computing actually entails. This article will clarify the differences between these quantum technologies.

What is Quantum Computing

Quantum computing refers specifically to using quantum mechanical phenomena like superposition and entanglement to perform operations on data. Quantum computers store information in quantum bits or “qubits” that can exist in superposition of 0 and 1 at the same time. When millions of qubits act together, they can deal with mind boggling amounts of information simultaneously using quantum parallelism. This gives quantum computers the potential to be millions of times faster than classical computers at certain complex tasks like optimization, machine learning and simulation.

Goals of Quantum Computing

The two main goals that researchers aim to achieve with quantum computers are:

  • To solve problems that classical computers practically cannot like breaking certain cryptographic codes or complex quantum physics simulations of large molecules and materials.
  • To massively speed up existing computing tasks from artificial intelligence to financial modeling and more. Major tech companies and startups are engaged in developing practical quantum algorithms and hardware for these purposes.

What are Quantum Simulators

A quantum simulator is a special purpose quantum computer designed to simulate quantum systems. These are systems like molecules, advanced materials or exotic phases of matter that follow the often strange and counterintuitive laws of quantum mechanics.

Accurately simulating large quantum systems is impractical even for the most powerful supercomputers. But tailor made quantum simulators leverage qubits and quantum effects to efficiently model other qubits and quantum effects. This means they can probe the properties and behaviors of quantum systems too complex for classical simulation.

Goals of Quantum Simulation

The main goals behind building quantum simulators are:

  • To study complex quantum systems relevant to fields like quantum chemistry, condensed matter physics, cosmology etc. This can lead to discovery of wonders like high temperature superconductors or new pharmaceutical molecules.
  • To test and troubleshoot qubit design and error correction strategies for general quantum computers. Building small special purpose simulators can guide development of scalable quantum hardware.
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So in summary quantum simulators are designed for modeling quantum systems, while general quantum computers have wider functionality.

What are Quantum Emulators

The term quantum emulator can have different specific meanings in different contexts. But in general it refers to using classical computation to mimic or approximate the results of an actual quantum computer. Quantum emulators leverage things like GPUs, clusters of specialized classical hardware, parallel computing frameworks like CUDA etc to simulate the working of quantum algorithms. But they do not use actual quantum phenomena or qubits. Think of them as software versions of quantum computers running on classical hardware. Their accuracy is inherently limited compared to real quantum computers due to not exploiting effects like entanglement.

Goals of Quantum Emulation

The motives behind development of quantum emulators include:

  • Allowing testing and refinement of quantum algorithms before real quantum hardware is available.
  • Trying to achieve “quantum advantage” i.e. do things faster than existing classical computers.
  • Understanding noise, errors and decoherence mechanisms that hurt performance of quantum processors.
  • Benchmarking classical supercomputer architectures on how well they can simulate quantum systems.

So in essence, quantum emulators act as stopgap software-based models while we await fully error-corrected quantum computers. They guide research into making those future systems as robust and practical as possible.

Comparison Table of Quantum Technologies

Here is a comparison table summarizing some key attributes of quantum computers, quantum simulators and quantum emulators:

So in short, quantum computers employ qubits to gain general performance advantages. Quantum simulators use qubits/quantum effects to study quantum systems. Quantum emulators try to imitate quantum systems’ output without qubits.

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Quantum Advantage

An important term that is often brought up while discussing these quantum information technologies is “quantum advantage“. This refers to achieving practical computational capabilities with quantum devices that go beyond what is possible clasically.

Out of the three systems we have discussed, only universal quantum computers have currently achieved modest quantum advantage with certain proof-of-principle benchmarks. Quantum simulators may offer some specialized advantages when modeling certain complex quantum setups. Quantum emulators do not offer true quantum advantage but might surpass previous classical techniques through massive parallelism.

Current State of Research

Quantum computing research has come a long way in recent years but still has challenges to overcome before commercialization. Some key points about where things currently stand across the quantum technology spectrum:

  • Quantum computers have progressed from few-qubit devices to ~100 qubit processors in labs. But we need millions of fault tolerant qubits for practical applications.
  • Quantum simulators with over 50 qubits exist but face similar scaling challenges. They however serve as prototypes for bigger quantum computers.
  • Quantum emulators running on supercomputers have simulated simple quantum circuits. But their limited accuracy leaves much scope for improvement.

So lots of foundational progress across the board but significant hardware and software innovations needed to build robust, large scale quantum information systems that deliver on the field’s promises.

Use Cases

Some promising near term use cases we can hope to tackle with these quantum-based technologies include:

  • Quantum computers: Optimization problems, quantum machine learning, quantum chemistry simulations etc.
  • Quantum simulators: High temperature superconductivity modeling, photosynthesis pathway mapping, nuclear fusion plasma analysis etc.
  • Quantum emulators: Cryptography, quantum algorithm development, precision metrology etc.

But the most transformative applications likely involve ideas and technologies we have not even conceived yet!

Challenges Faced

Despite great excitement and progress, many challenges remain to realize the potential of quantum technologies:

  • Building reliable qubits that maintain quantum coherence for sufficiently long times without error remains hard. This impacts scaling.
  • We need major algorithmic and software breakthroughs to unlock the true power of quantum hardware.
  • Seamlessly integrating quantum and classical computing paradigms for ideal hybrid performance requires research.
  • Widespread skill development in quantum information science across industry and academia also lags behind hardware advancements.
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With sufficient investment and innovation resolving the above roadblocks over the next decade, we could witness profound impacts from the quantum computing revolution on both science and society!


To conclude quantum computing uses quantum mechanics like superposition and entanglement to gain advantages in computation speed and tackling formerly intractable problems. Quantum simulators employ tailor made qubits and quantum effects to efficiently simulate complex quantum systems for research breakthroughs. Quantum emulators try to mimic the results of quantum computers through sheer classical computational power alone.

While the practical realization of quantum technologies still faces hardware and software challenges, tremendous progress has been made in recent years in both academic and commercial spheres. This sets the stage for their potentially transformative influence on everything from medical research to machine learning in coming years if key technical hurdles can be overcome. Harnessing the bizarre workings of quantum physics for computation remains one of the most exciting and rapidly evolving interdisciplinary pursuits of the 21st century.


How are quantum simulators different from analog quantum computers?

Quantum simulators refer to special purpose quantum computation devices for modeling quantum systems. Analog quantum computers are aiming to build general purpose quantum computers using analog components rather than digital qubits. So they target different applications but both leverage quantum effects.

Can quantum emulators prove theorems like quantum computers someday?

Quantum emulators use classical hardware to approximate quantum systems, but cannot exploit unique quantum effects like entanglement. This limits their capabilities versus actual quantum computers.

What was the first commercial quantum computer?

In 2011 D-Wave systems developed the first commercial quantum annealer specialized for optimization problems. It was based on quantum annealing rather than gate model quantum computing.

Are quantum simulator algorithms easy to adapt to universal quantum computers?

Yes, since quantum simulation builds intuition about quantum systems. But specialized simulator hardware differs, so the algorithms need recasting for general quantum computers.

Can classical machine learning match quantum machine learning?

Unlikely in the long run. Quantum machine learning using quantum neural networks exploits quantum parallelism for exponential speedups over classical techniques ultimately.