Editorial Feature

Surface Metrology from a Quantum Perspective

Article Updated on 19 April 2021

Farhads / Shutterstock

Surface metrology is the branch of metrology that focuses on the minute features of physical surfaces, such as the surface’s primary form (overall shape), fractality (pattern changes at various levels of detail), and roughness (level of deviation from the normal vector of its ideal form).

Classical surface metrology techniques include contact measurement, which involves dragging a stylus over the surface with a piece of equipment called a profilometer, and non-contact measurements involving light waves, electrons, or photographic images.

Recent advances in quantum physics have opened up a new generation of metrology and surface metrology techniques, which enable much more precise measurements with higher resolution and greater sensitivity.

Overcoming the limitations of classical metrology

Quantum metrology and quantum surface metrology exploit the peculiar quantum mechanical effects of quantum entanglement and quantum squeezing.

Quantum entanglement is the observed tendency of multiple quantum particles becoming linked to one another regardless of the distance between them. Spinning one particle causes another entangled particle to spin as well.

Quantum squeezing moves the uncertainty of an entire system, from the area that the metrologist wants to measure to another part of the system that does not need to be measured, without having to reduce the overall uncertainty in the system. This is similar to squeezing the air from one end of a balloon to another.

Quantum surface metrology techniques that exploit these non-classical physical effects have recently been shown to overcome the extreme limit of image resolution, which is defined as the minimum distance between two light sources before they become indistinguishable from one another. This limitation is known as Rayleigh’s criterion.

Surface metrology with quantum entanglement

One quantum metrology technique utilizing the effect of quantum entanglement that overcomes the Rayleigh criterion involves the NOON state of light. The NOON state is a multipartite (containing multiple particles) state of photons (or theoretically any Bosonic field particle) in which the photons are related.

In the technique, the NOON state is achieved in a Mach-Zehnder interferometer to produce a surface measurement. In one study, it was shown that this technique could enhance accuracy in surface metrology as well as image resolution in quantum lithography (Kok, Braunstein and Dowling, 2004).

Techniques exploiting quantum entanglement in the NOON state can distinguish between light sources closer than the minimum possible distance set out in the Rayleigh criterion. It has been shown that using quantum entanglement-based techniques in multipartite systems such as this, is necessary to achieve maximum sensitivity in surface measurements (Tóth, 2012).

Surface metrology with quantum squeezing

A recent development from a team of physicists at the National Institute of Standards and Testing (NIST), utilizes quantum squeezing to “measure with greater sensitivity than could be achieved without quantum effects”, according to the study’s lead author (Ost, 2019).

The method traps a single ion 30 micrometers above a flat sapphire chip and controls it with gold electrons which cover the surface of the sapphire. Electric signals are used to achieve the squeezed state in the system and move the ion, and then to reverse the squeezing and generate magnetic fields which can be used to measure the motion (Burd et al., 2019).

This method was shown to ion motions of only 50 picometers (trillionths of a meter), and repeating the steps can produce even more minute surface measurements.

The new method put forward by the NIST team not only advances the burgeoning fields of quantum metrology, quantum surface metrology, and quantum information science, but it can also be applied to other sciences exploiting quantum mechanics such as quantum computing.

This is due to its previously unachieved levels of amplification, meaning that larger systems can be measured than were previously possible. This can help quantum computers operate much more quickly, and can also speed up the quantum simulation.


  • Burd, S.C., Srinivas, R., Bollinger, J.J., Wilson, A.C., Wineland, D.J., Leibfried, D., Slichter, D.H., and Allcock, D.T.C. (2019). Quantum amplification of mechanical oscillator motion. Science, 364(6446), pp.1163–1165.
  • Kok, P., Braunstein, S.L., and Dowling, J.P. (2004). Quantum lithography, entanglement, and Heisenberg-limited parameter estimation. Journal of Optics B: Quantum and Semiclassical Optics, 6(8), pp.S811–S815.
  • Ost, L. (2019). NIST Team Supersizes ‘Quantum Squeezing’ to Measure Ultrasmall Motion. [online] NIST. Available at: https://www.nist.gov/news-events/news/2019/06/nist-team-supersizes-quantum-squeezing-measure-ultrasmall-motion [Accessed 21 Sep. 2019].
  • Tóth, G. (2012). Multipartite entanglement and high-precision metrology. Physical Review A, 85(2).

Disclaimer: The views expressed here are those of the author expressed in their private capacity and do not necessarily represent the views of AZoM.com Limited T/A AZoNetwork the owner and operator of this website. This disclaimer forms part of the Terms and conditions of use of this website.

Ben Pilkington

Written by

Ben Pilkington

Ben Pilkington is a freelance writer who is interested in society and technology. He enjoys learning how the latest scientific developments can affect us and imagining what will be possible in the future. Since completing graduate studies at Oxford University in 2016, Ben has reported on developments in computer software, the UK technology industry, digital rights and privacy, industrial automation, IoT, AI, additive manufacturing, sustainability, and clean technology.


Please use one of the following formats to cite this article in your essay, paper or report:

  • APA

    Pilkington, Ben. (2021, April 19). Surface Metrology from a Quantum Perspective. AZoQuantum. Retrieved on June 21, 2024 from https://www.azoquantum.com/Article.aspx?ArticleID=159.

  • MLA

    Pilkington, Ben. "Surface Metrology from a Quantum Perspective". AZoQuantum. 21 June 2024. <https://www.azoquantum.com/Article.aspx?ArticleID=159>.

  • Chicago

    Pilkington, Ben. "Surface Metrology from a Quantum Perspective". AZoQuantum. https://www.azoquantum.com/Article.aspx?ArticleID=159. (accessed June 21, 2024).

  • Harvard

    Pilkington, Ben. 2021. Surface Metrology from a Quantum Perspective. AZoQuantum, viewed 21 June 2024, https://www.azoquantum.com/Article.aspx?ArticleID=159.

Tell Us What You Think

Do you have a review, update or anything you would like to add to this article?

Leave your feedback
Your comment type

While we only use edited and approved content for Azthena answers, it may on occasions provide incorrect responses. Please confirm any data provided with the related suppliers or authors. We do not provide medical advice, if you search for medical information you must always consult a medical professional before acting on any information provided.

Your questions, but not your email details will be shared with OpenAI and retained for 30 days in accordance with their privacy principles.

Please do not ask questions that use sensitive or confidential information.

Read the full Terms & Conditions.