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Counting electrons

Understanding the science

Is counting every electons really necessary?

Most measurements of large current don’t need the extreme accuracy of microscopic electron counting 🧑‍🔬, but there are some really important reasons why it is a neat technology.🔬🧬📡 🛰 🪐🚀

As far as we know, all of the electrons on earth 🌍 and in the universe 🪐 are exactly the same. This makes electron-counting a route to a standard that is truly 'universal'. It doesn’t matter exactly which electrons you count or where, or when. This robustness and universality is particularly valuable on the frontiers of science and technology, where other things are unknown.

Scientists 👩‍💻 are often trying to discover new things, improve people’s health, protect the planet and other lofty goals. This often means measuring and interpreting sensor signals. Sometimes these signals are really tiny and difficult to measure accurately - environmental sensors are often like this. Standards for small current, including electron counting, will help make this sensor data meaningful.

Do you ever make mistakes when you are counting the electrons?

We engineer and control our single electron trap so that it 'almost certainly' moves a single electron in every tick of our pumping clock 🕜. But what do we mean by 'almost certainly'?

We spend a lot of time measuring how close to perfect our electron counting can get. At the moment we think we can make less than one mistake (a missing or extra electron) in every million cycles. If you can count to 1 million and make zero mistakes then you are doing better than us. This accuracy is already good enough for some measurement problems and has helped us make more accurate measurements.

What is 'quantum' anyway?

Quantum physics explains the behaviour of atoms, eletrons and photons. It is famous (or infamous) for being a bit tricky to understand and counter-intuitive. It causes endless debates over whether 'stuff' is more 'wave-like' or 'particle-like'. Regardless of its apparent weirdness, quantum physics has enabled the development of semiconductor electronics, lasers and many other essential technologies.

Importantly for a metrologist, quantum physics gives access to unchanging measurement standards - not just electricity but in all physical measurements. The electron <Add another sentence explaining the connection between electron pumps and quantum technology more generally>

Are quantum standards really better than old standards?

There is some nostalgia for old fashioned metrology tools…such as a metal rod to define length and mass or a chemical battery to define the voltage standard. This might feel easier to understand, but this 'old school' approach is full of pitfalls. Artefacts, or physical standards, change with measurement conditions, handling or just time. This creates practical problems and accuracy limitations when using them for calibration or real world measurements.

Quantum standards look more complicated, but they are inherently stable. Because physical laws are perfectly reproducible, each quantum standard behaves in EXACTLY the same way. You can’t 'copy and paste' artefacts and make them exactly the same, but you can with quantum standards. 

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What is quantum?

Quantum physics describes the properties of atoms, electrons and photons which can behave either like waves or particles, resulting in many extraordinary properties. Quantum technologies can provide unchanging measurement standards and 'quantum behaviour’ can potentially create a completely new class of advanced environmental sensors and systems. These radically new capabilities will be used in timing and navigation, secure communications, driverless cars, computing and other critical applications.

NPL carries out quantum research, ensures the metrology framework is in place for innovative devices and develops testing and measurement techniques. We provide the expertise and facilities needed to underpin the development of quantum technologies in the UK.

Quantum technologies

The NPL Quantum Programme

Understanding quantum science

Explore the world of measurement with our app

This app is an exciting way to explore the world of measurement and have some fun, learning a thing or two along the way! Download the app and accompanying poster pack to join the quest!

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