The Nobel Prize 2023 (Physics and Chemistry) winners’ research – the intersection of attosecond physics and the evolution of quantum dots heralds a new era in the temporal frontier of science; where the minutiae of time and the infinitesimal scale of materials unlock profound technological potentials.
Attosecond physics, or AttoPhysics, delves into the complex domain of processes transpiring on an attosecond timescale.
1 attosecond=10-18seconds
In simple words, it can be conceptualised as a billionth of a billionth fraction of a second.
Attosecond physics emerged as a field in the early 2000s, however, the foundational groundwork can be traced back to the 1940s with transistor innovations in the field of transistor and microwave electronics.
During the Second World War, microwave engineering played a critical role in developing radar that could accurately locate enemy ships and planes with a focused beam of electromagnetic radiations.
The curiosity to reduce the pulse duration resulted in achieving microwave pulses spanning from microseconds 10-6 to picoseconds 10-12. Pushing beyond femtoseconds 10-15 proved challenging, but the progression towards attosecond realms is nothing short of astounding.
The below example provides further understanding of how small is 1 attosecond
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An attosecond is so short that that the number of them in one second is the same as the number of seconds that have elapsed since the universe came into existence, 13.8 billion years ago.
Source: https://www.nobelprize.org/uploads/2023/11/popular-physicsprize2023-1.pdf
Our natural observation capabilities marvel at macroscopic phenomena, but the true intrigue lies in the ultra-microscopic and ultra-rapid. This is where the magic of attosecond physics reveals itself.
Electrons’ movements in atoms and molecules are so rapid that they are measured in attoseconds. An attosecond is to one second as one second is to the age of the universe.
Why it is important for us to have fast processes
We can understand it with a daily life example. Capturing a photo of a fast-moving object becomes blurry because the object changes its frame faster than the camera’s shutter speed.
A similar thing happens at the ultra-small size when we try to be imaging electrons, we cannot because it is too fast and faster than the process of imaging. This is where the attosecond pulses will help imaging of ultra small size objects. Light can travel from one atom to its neighbouring atom in one attosecond.
Before an attosecond pulse, scientists could study the dynamics of systems like atoms, molecules or compounds with femtosecond (10-15) pulses. The study of detailed dynamics of electrons was not possible with femtoseconds because it is ultra small and ultra-fast in nature. An electron is a vital component in the physical and chemical process of matter.
The formation or deformation of compounds starts with an electron's movement; electrons play a key role in the photosynthesis process to prepare food in plants or in photovoltaic cells to generate electric current in solar cells. An atosecond pulse makes it possible for imaging the movement of electrons in real time.
Besides biology and chemistry, another promising application is electronics. In running age, the electronic circuits switch ON and OFF at a nanosecond scale.
The switching makes the information processing possible through an electronic circuit, the faster the switching, the faster the processing speed of the electronic circuit. Current electronic circuit switching speed is approximately six billion times in a second or simply we say 6 Giga-Hertz (109) speed.
But theoretically, taking advantage of attosecond physics, the possible switching speed is in Peta-Hertz (1015) which means trillion times switching in one second. Researchers are exploring this field to reach petahertz electronics, which means there will be about 100 thousand times faster computers than today.
Quantum computer and quantum sensing are the potential applications of Attosecond science. It fundamentally involves quantum mechanics, through which it is possible to measure quantum processes directly.
Attosecond pulses help to precisely manipulate electrons in atoms or molecules, which is an important factor in quantum computing to make qubit (quantum bit) able to process information.
Attosecond pulse can accurately detect the state of a qubit like superposition or entanglement. and it can help to prepare quantum gates which are the building blocks for quantum computing. A major hindrance in today’s quantum computer development is its susceptibility to errors and decoherence which can be mitigated with attosecond pulse.
The Nobel prize 2023 in physics winning trio of scientists developed the way to generate attosecond pulses. It opened a huge avenue of research to understand the dynamics of electrons; how electrons transfer charges, how they become positive or negative ions.
How electrons of one element attract another element to make a new compound. It is possible to track how its shape evolves in real time. Attosecond physics provides support to the development of classical computers to the next level and paves the path for quantum computing. It is potential enough to revolutionise many other areas of science and technology.
Chemistry
The characteristics of a substance are determined by its chemical composition. However, when a material reaches the scale of nanometres, its size also influences its colour and other attributes.
Quantum dots are nanoscale semiconductor particles that have unique optical and electronic properties due to their quantum mechanical effects.
The size and shape of these particles can be finely tuned during synthesis, which directly affects their colour and brightness. This size-dependent property arises from the quantum confinement effect, where the motion of electrons and holes (the absence of electrons) is restricted to a very small space, leading to discrete energy levels.
When excited by light, these particles emit light of specific colours, which depend on their size – smaller dots emit blue light, while larger ones emit red. This size-dependent behaviour occurs because quantum dots confine electrons and holes in all three dimensions, creating discrete energy levels.
Quantum dots are nanoparticles but not every nanoparticle is a quantum dot. Only some materials (such as semiconductors) will show quantum size effects in their electronic structure when they are made into nanoscale particles.
Source: https://www.istockphoto.com/photo/quantum-dots-of-different-size-gm177724100-24034646?utm_source=pixabay&utm_medium=affiliate&utm_campaign=SRP_image_sponsored&utm_content=https%3A%2F%2Fpixabay.com%2Fimages%2Fsearch%2Fquantum%2520dots%2F&utm_term=quantum+dots
Quantum dots exhibit high brightness, pure colour emission, and long-lasting stability, making them valuable in various applications, including:
- Displays: quantum dots are used in display technologies to produce TVs and monitors with vibrant colours and energy efficiency. They enable a wider colour gamut and improved brightness compared to traditional display materials;
- Medical imaging: due to their bright and tenable emission, quantum dots can be used for fluorescent biological labelling, allowing researchers to track the movement of molecules within organisms with high precision;
- Photovoltaics: quantum dots can be applied in solar cells to improve light absorption and efficiency by utilising a broader spectrum of sunlight.
- Quantum computing: Their unique quantum properties make them potential candidates for use in quantum computing as qubits, the basic unit of quantum information;
- LED lighting: quantum dots can be used to create highly efficient and tenable LED lights, offering a broad range of colours and improved colour rendering.
The production and use of quantum dots are subjects of active research, aiming to optimise their synthesis, understand their properties better, and expand their applications across various scientific and industrial fields.
This concept was theoretically understood, but Alexey Ekimov provided a pivotal experimental proof during his investigation of coloured glass. Ekimov noticed the changing colours of copper chloride containing glass, changing with duration and intensity of the heating process.
In 1981, he reported this work in a Soviet scientific publication, based on X-ray analysis which showed that the change in colours was due to changes in the size of the copper chloride microcrystals.
Later, at Bell Laboratories in the United States, Louis Brus observed variation in particles' optical properties attributing to particle growth, a phenomenon driven by a quantum effect related to size. Louis Brus was exploring how to harness solar energy for chemical reactions involving small cadmium sulphide particles in a solution.
In 1993, Moungi Bawendi further advanced the chemical synthesis of quantum dots, creating nearly perfect particles with controllable sizes. This breakthrough in manufacturing techniques opened the doors for broader commercial and medical uses of quantum dots.
The journey from the theoretical underpinnings of quantum dots to the experimental breakthroughs in attosecond physics encapsulates a remarkable narrative of scientific innovation.
It underscores the pivotal role of size and time in determining material properties and their implications for future technologies. The synthesis of nearly perfect quantum dots by Moungi Bawendi and the advent of attosecond pulses have catalysed a paradigm shift in how we visualise and manipulate the quantum world.
The scientific community and quantum nerds are eagerly awaiting 2024 Nobel Prize in Physics and Chemistry (announced in the second week of October).
Hoping for more breakthroughs, bringing us one step closer to the reality of quantum computing age. As these areas of research evolve, they hold the potential to revolutionise computing, making quantum computers a tangible part of our future.
References
https://www.theguardian.com/science/2023/oct/04/nobel-prize-in-chemistry-winners-2023
https://www.forbes.com/sites/saleemali/2023/10/01/nobel-prizes-science-and-islam/
https://www.nobelprize.org/uploads/2023/11/popular-physicsprize2023-1.pdf
https://www.electrooptics.com/feature/attosecond-science-all#:~:text=In%20today's%20electronic%20circuits%2C%20electrons,occurring%20at%20the%20attosecond%20scale
https://www.cecam.org/workshop-details/18#:~:text=Its%20main%20objective%20is%20to,processing%20in%20human%2Dmade%20devices
https://www.nature.com/articles/s41467-019-09036-w
https://www.laserfocusworld.com/lasers-sources/article/14299729/2023-nobel-prize-in-physics-recognizes-methods-to-generate-attosecond-pulses-of-light
https://www.youtube.com/watch?v=Xvb6vysV5Pg&ab_channel=TomDouglas-Walker
https://theconversation.com/what-is-an-attosecond-a-physical-chemist-explains-the-tiny-time-scale-behind-nobel-prize-winning-research-214907
https://www.insidequantumtechnology.com/news-archive/how-attosecond-laser-pulses-recognized-by-2023-nobel-prize-in-physics-influences-quantum-computing/#: ~:text=Attosecond%20laser%20pulses%20can%20help, qubits%20in%20specific%20quantum%20state
Authors: Lala Rukh (LinkedIn) is a doctoral researcher in MaREI–Science Foundation Ireland Research Centre for Energy, Climate and Marine Research and Innovation at the University of Galway. She is an electrical engineer and has master's degrees in energy systems and marine plastics abatement. Abdul Fatah (LinkedIn) is PhD researcher in the area quantum computing algorithms at Atlantic Technological University Galway, Ireland. Currently, he is developing new algorithms for Noisy Intermediate scale quantum (NISQ) era quantum computers as well as envision the algorithms for future fault-tolerant quantum computers. And Muhammad Mohsin (LinkedIn) is Computational Sciences and Engineering student at the National University of Sciences and Technology (NUST), Pakistan.