̽��ֱ�� of Cambridge - atom

A peek inside the box that could help solve a quantum mystery

sc604 — Tue, 19 Nov 2024 15:22:24 +0000

Appearing as ‘bumps’ in the data from high-energy experiments, these signals came to be known as short-lived ‘XYZ states.’ They defy the standard picture of particle behaviour and are a problem in contemporary physics, sparking several attempts to understand their mysterious nature.

But theorists at the U.S. Department of Energy’s Thomas Jefferson National Accelerator Facility in Virginia, with colleagues from the ̽��ֱ�� of Cambridge, suggest the experimental data could be explained with fewer XYZ states, also called resonances, than currently claimed.

̽��ֱ��team used a branch of quantum physics to compute the energy levels, or mass, of particles containing a specific ‘flavour’ of the subatomic building blocks known as quarks. Quarks, along with gluons, a force-carrying particle, make up the Strong Force, one of the four fundamental forces of nature.

̽��ֱ��researchers found that multiple particle states sharing the same degree of spin – or angular momentum – are coupled, meaning only a single resonance exists at each spin channel. This new interpretation is contrary to several other theoretical and experimental studies.

̽��ֱ��researchers have presented their results in a pair of companion papers published for the international Hadron Spectrum Collaboration (HadSpec) in Physical Review Letters and Physical Review D. ̽��ֱ��work could also provide clues about an enigmatic particle: X(3872).

̽��ֱ��charm quark, one of six quark ‘flavours’, was first observed experimentally in 1974. It was discovered alongside its antimatter counterpart, the anticharm, and particles paired this way are part of an energy region called ‘charmonium.’

In 2003, Japanese researchers discovered a new charmonium candidate dubbed X(3872): a short-lived particle state that appears to defy the present quark model.

“X(3872) is now more than 20 years old, and we still haven’t obtained a clear, simple explanation that everyone can get behind,” said lead author Dr David Wilson from Cambridge’s Department of Applied Mathematics and Theoretical Physics (DAMTP).

Thanks to the power of modern particle accelerators, scientists have detected a hodgepodge of exotic charmonium candidate states over the past two decades.

“High-energy experiments started seeing bumps, interpreted as new particles, almost everywhere they looked,” said co-author Professor Jozef Dudek from William & Mary. “And very few of these states agreed with the model that came before.”

But now, by creating a tiny virtual ‘box’ to simulate quark behaviour, the researchers discovered that several supposed XYZ particles might actually be just one particle seen in different ways. This could help simplify the confusing jumble of data scientists have collected over the years.

Despite the tiny volumes they were working with, the team required enormous computing power to simulate all the possible behaviours and masses of quarks.

̽��ֱ��researchers used supercomputers at Cambridge and the Jefferson Lab to infer all the possible ways in which mesons – made of a quark and its antimatter counterpart – could decay. To do this, they had to relate the results from their tiny virtual box to what would happen in a nearly infinite volume – that is, the size of the universe.

“In our calculations, unlike experiment, you can't just fire in two particles and measure two particles coming out,” said Wilson. “You have to simultaneously calculate all possible final states, because quantum mechanics will find those for you.”

̽��ֱ��results can be understood in terms of just a single short-lived particle whose appearance could differ depending upon which possible decay state it is observed in.

“We're trying to simplify the picture as much as possible, using fundamental theory with the best methods available,” said Wilson. “Our goal is to disentangle what has been seen in experiments.”

Now that the team has proved this type of calculation is feasible, they are ready to apply it to the mysterious particle X(3872).

“ ̽��ֱ��origin of X(3872) is an open question,” said Wilson. “It appears very close to a threshold, which could be accidental or a key part of the story. This is one thing we will look at very soon."

Professor Christopher Thomas, also from DAMTP, is a member of the Hadron Spectrum Collaboration, and is a co-author on the current studies. Wilson’s contribution was made possible in part by an eight-year fellowship with the Royal Society. ̽��ֱ��research was also supported in part by the Science and Technology Facilities Council (STFC), part of UK Research and Innovation (UKRI). Many of the calculations for this study were carried out with the support of the Cambridge Centre for Data Driven Discovery (CSD3) and DiRAC high-performance computing facilities in Cambridge, managed by Cambridge’s Research Computing Services division.

Reference:
David J. Wilson et al. ‘Scalar and Tensor Charmonium Resonances in Coupled-Channel Scattering from Lattice QCD.’ Physical Review Letters (2024). DOI: 10.1103/PhysRevLett.132.241901

David J. Wilson et al. ‘Charmonium xc0 and xc2 resonances in coupled-channel scattering from lattice QCD.’ Physical Review D (2024). DOI: 10.1103/PhysRevD.109.114503

Adapted from a Jefferson Lab story.

An elusive particle that first formed in the hot, dense early universe has puzzled physicists for decades. Following its discovery in 2003, scientists began observing a slew of other strange objects tied to the millionths of a second after the Big Bang.

gremlin via Getty Images

Abstract colourful lines

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New result from LHCb experiment challenges leading theory in physics

sc604 — Tue, 23 Mar 2021 09:42:57 +0000

Results from the LHCb Collaboration at CERN suggests particles are not behaving the way they should according to the guiding theory of particle physics – suggesting gaps in our understanding of the Universe.

Physicists from the Universities of Cambridge, Bristol, and Imperial College London led the analysis of the data to produce this result, with funding from the Science and Technology Facilities Council. ̽��ֱ��result - which has not yet been peer-reviewed - was announced today at the Moriond Electroweak Physics conference and published as a preprint.

Beyond the Standard Model

Scientists across the world will be paying close attention to this announcement as it hints at the existence of new particles not explained by the Standard Model.

̽��ֱ��Standard Model is the current best theory of particle physics, describing all the known fundamental particles that make up our Universe and the forces that they interact with. However, the Standard Model cannot explain some of the deepest mysteries in modern physics, including what dark matter is made of and the imbalance of matter and antimatter in the Universe.

Dr Mitesh Patel of Imperial College London, and one of the leading physicists behind the measurement, said: “We were actually shaking when we first looked at the results, we were that excited. Our hearts did beat a bit faster.

“It’s too early to say if this genuinely is a deviation from the Standard Model but the potential implications are such that these results are the most exciting thing I’ve done in 20 years in the field. It has been a long journey to get here.”

Building blocks of nature

Today’s results were produced by the LHCb experiment, one of four huge particle detectors at CERN’s Large Hadron Collider (LHC).

̽��ֱ��LHC is the world’s largest and most powerful particle collider – it accelerates subatomic particles to almost the speed of light, before smashing them into each other.

These collisions produces a burst of new particles, which physicists then record and study in order to better understand the basic building blocks of nature.

̽��ֱ��LHCb experiment is designed to study particles called ‘beauty quarks’, an exotic type of fundamental particle not usually found in nature but produced in huge numbers at the LHC.

Once the beauty quarks are produced in the collision, they should then decay in a certain way, but the LHCb team now has evidence to suggest these quarks decay in a way not explained by the Standard Model.

Questioning the laws of physics

̽��ֱ��updated measurement could question the laws of nature that treat electrons and their heavier cousins, muons, identically, except for small differences due to their different masses.

According to the Standard Model, muons and electrons interact with all forces in the same way, so beauty quarks created at LHCb should decay into muons just as often as they do to electrons.

But these new measurements suggest this is not happening.

One way these decays could be happening at different rates is if never-before-seen particles were involved in the decay and tipped the scales in favour of electrons.

Dr Paula Alvarez Cartelle from Cambridge’s Cavendish Laboratory, was one of the leaders of the team that found the result, said: “This new result offers tantalising hints of the presence of a new fundamental particle or force that interacts differently with these different types of particles.

“ ̽��ֱ��more data we have, the stronger this result has become. This measurement is the most significant in a series of LHCb results from the past decade that all seem to line up – and could all point towards a common explanation.

“ ̽��ֱ��results have not changed, but their uncertainties have shrunk, increasing our ability to see possible differences with the Standard Model.”

Not a foregone conclusion

In particle physics, the gold standard for discovery is five standard deviations – which means there is a 1 in 3.5 million chance of the result being a fluke. This result is three deviations – meaning there is still a 1 in 1000 chance that the measurement is a statistical coincidence.

It is therefore too soon to make any firm conclusions. However, while they are still cautious, the team members are nevertheless excited by this apparent deviation and its potentially far-reaching implications.

̽��ֱ��LHCb scientists say there has been a breadcrumb trail of clues leading up to this result – with a number of other, less significant results over the past seven years also challenging the Standard Model in a similar way, though with less certainty.

If this result is what scientists think it is – and hope it is – there may be a whole new area of physics to be explored.

Dr Konstantinos Petridis of the ̽��ֱ�� of Bristol, who also played a lead role in the measurement, said: “ ̽��ֱ��discovery of a new force in nature is the holy grail of particle physics. Our current understanding of the constituents of the Universe falls remarkably short – we do not know what 95% of the Universe is made of or why there is such a large imbalance between matter and anti-matter.

“ ̽��ֱ��discovery of a new fundamental force or particle, as hinted at by the evidence of differences in these measurements could provide the breakthrough required to start to answer these fundamental questions.”

Dr Harry Cliff, LHCb Outreach Co-Convener, from Cambridge’s Cavendish Laboratory, said: “This result is sure to set physicists’ hearts beating a little faster today. We’re in for a terrifically exciting few years as we try to figure out whether we’ve finally caught a glimpse of something altogether new.”

It is now for the LHCb collaboration to further verify their results by collating and analysing more data, to see if the evidence for some new phenomena remains.

Additional information – about the result

̽��ֱ��results compare the decay rates of Beauty mesons into final states with electrons with those into muons.

̽��ֱ��LHCb experiment is one of the four large experiments at the Large Hadron Collider (LHC) at CERN in Geneva, and is designed to study decays of particles containing a beauty quark

This is the quark with the highest mass forming bound states. ̽��ֱ��resulting precision measurements of matter-antimatter differences and rare decays of particles containing a beauty quark allow sensitive tests of the Standard Model of particle physics.

Rather than flying out in all directions, beauty quarks that are created in the collisions of the proton beams at LHC stay close to the beam pipe.

̽��ֱ��UK team studied a large number of beauty or b quarks decaying into a strange-quark and two oppositely charged leptons. By measuring how often the b-quark decays into a final state containing a pair of muons or a pair of electrons, they found evidence that the laws of physics might be different, depending on whether the final state contains electrons or muons.

Since the b-quark is heavy compared to the masses of the electron and muon it is expected that the b-quark decays with the same probability into a final state with electrons and muons. ̽��ֱ��ratio between the two decay probabilities is hence predicted to be one.

However analysis of the UK team found evidence that the decay probability is less than one.

UK particle physicists have today announced ‘intriguing’ results that potentially cannot be explained by the current laws of nature.

This new result offers tantalising hints of the presence of a new fundamental particle or force that interacts differently with these different types of particles.

Paula Alvarez Cartelle

CERN

LHCb experiment

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Revealing the personal side of the atomic scientist who changed the world

sjr81 — Fri, 22 Sep 2017 08:56:28 +0000

Sir John Cockcroft was one of the most important and influential scientists of the modern era. He was the joint winner of the Nobel Prize for Physics (1951) for his pioneering work at the Cavendish Laboratory on the disintegration of atoms (splitting the atom).

His research facilitated the development of atomic power, nuclear medicine and accelerator science. He was the first Director of the British Atomic Energy Research Establishment at Harwell, and the first Master of Churchill College, Cambridge.

This evening, several generations of the Cockcroft family, including Sir John’s surviving children, will gather at Churchill College to celebrate the 120th anniversary of Sir John’s birth and the 50th of his death.

They will mark the occasion by handing over to the Churchill Archives Centre a family treasure trove of scrapbooks, photograph albums and hitherto unseen diaries and letters from the Western Front of World War One, illustrating the personal life of this most public scientist.

Here, it will join his Nobel Prize medal and complement his scientific papers, including his notebooks for his ground-breaking experiments which are already housed at the Archive Centre. ̽��ֱ��new material includes 400 letters to his fiancée from 1915-1919, along with a mass of later correspondence, including letters to his mother during his high powered scientific roles in the Second World War.

Other highlights include:

Scrapbooks containing material on the Tizard mission (1940) which gave the Americans, on Churchill's orders, our scientific secrets regarding the possibility of making an atomic bomb and the newly invented cavity magnetron. Sir Henry Tizard led the mission with John Cockcroft as his deputy.
Gamov's letter to Cockcroft of 7th September 1932, congratulating him on his discovery (first artificial disintegration of atomic nuclei).
Sir John’s WW1 diaries from the Western Front.

After completing his first year at Manchester ̽��ֱ��, John Cockcroft left home in the summer of 1915 during World War One. Too young to enlist, he first worked as a YMCA volunteer in an Army Camp at Abergele. In 1916 he joined the Royal Field Artillery (RFA) as a Private. He became a signaller in the RFA and was sent to France to join the latter stages of the Battle of the Somme.

Subsequently he moved in July 1917 for the 3rd Battle of Ypres, known as Passchendaele. He survived unscathed throughout, even though many fellow soldiers in his Battery were killed or wounded. Early in 1918 he went back to England to train as an officer, which is where he was when the war ended in November 1918.

A complete set of nearly 400 letters home exist covering the whole of this period. Together they amount to a wonderfully descriptive and insightful account of unstinting service to his country. In addition there are some pocket diaries which he kept, despite regulations forbidding them.

Dame Athene Donald, Master of Churchill College, said: “Both as Master and as professor of Experimental Physics at the ̽��ֱ�� of Cambridge, I am conscious that I owe a great personal debt to Sir John. But it is fair to say that his work has had a lasting legacy which continues to influence us all. This new material will sit alongside his existing scientific papers in the Archives Centre and will enable future generations to know the man behind the scientist.”

Christopher Cockcroft, Sir John’s son, said, “ ̽��ֱ��time was right for the family to share this material and for it to be conserved for future generations to learn the full story of this remarkable man: a secondary school boy from Todmorden, who survived the First World War, and worked his way to the top of his profession; a man who firmly believed in the fellowship of man and did much to foster understanding between people and nations.”

Michael Smyth, author of a forthcoming biography of Sir John, highlighted the set of scrapbooks kept by Sir John’s mother and the many letters to his wife which together provide a unique insight into his life.

̽��ֱ��reception and handover will take place in the Jock Colville Hall, Churchill College at from 6pm on Friday evening (September 22). All are welcome. ̽��ֱ��event will mark the beginning of the Churchill College Alumni Association Weekend, and will be the first of several events during the weekend celebrating Sir John’s life and legacy.

See https://www.chu.cam.ac.uk/events/churchill-college-association-weekend-2... for further details.

War diaries, scrapbooks, letters and photographs belonging to Sir John Cockcroft, Nobel Prize winner and one of the most influential scientists of the modern era, will today be placed in the care of the Churchill Archives Centre.

Cockroft's work has had a lasting legacy which continues to influence us all. This new material will sit alongside his existing scientific papers in the Archives Centre and will enable future generations to know the man behind the scientist.

Athene Donald

Sir John and Lady Cockcroft at home circa 1946. From left to right: Elisabeth, Catherine, Lady Cockcroft, Jocelyn, Sir John Cockcroft, Dorothea and Christopher.

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World’s 'smallest magnifying glass' makes it possible to see individual chemical bonds between atoms

sc604 — Thu, 10 Nov 2016 19:00:00 +0000

For centuries, scientists believed that light, like all waves, couldn’t be focused down smaller than its wavelength, just under a millionth of a metre. Now, researchers led by the ̽��ֱ�� of Cambridge have created the world’s smallest magnifying glass, which focuses light a billion times more tightly, down to the scale of single atoms.

In collaboration with European colleagues, the team used highly conductive gold nanoparticles to make the world’s tiniest optical cavity, so small that only a single molecule can fit within it. ̽��ֱ��cavity – called a ‘pico-cavity’ by the researchers – consists of a bump in a gold nanostructure the size of a single atom, and confines light to less than a billionth of a metre. ̽��ֱ��results, reported in the journal Science, open up new ways to study the interaction of light and matter, including the possibility of making the molecules in the cavity undergo new sorts of chemical reactions, which could enable the development of entirely new types of sensors.

According to the researchers, building nanostructures with single atom control was extremely challenging. “We had to cool our samples to -260°C in order to freeze the scurrying gold atoms,” said Felix Benz, lead author of the study. ̽��ֱ��researchers shone laser light on the sample to build the pico-cavities, allowing them to watch single atom movement in real time.

“Our models suggested that individual atoms sticking out might act as tiny lightning rods, but focusing light instead of electricity,” said Professor Javier Aizpurua from the Center for Materials Physics in San Sebastian in Spain, who led the theoretical section of this work.

“Even single gold atoms behave just like tiny metallic ball bearings in our experiments, with conducting electrons roaming around, which is very different from their quantum life where electrons are bound to their nucleus,” said Professor Jeremy Baumberg of the NanoPhotonics Centre at Cambridge’s Cavendish Laboratory, who led the research.

̽��ֱ��findings have the potential to open a whole new field of light-catalysed chemical reactions, allowing complex molecules to be built from smaller components. Additionally, there is the possibility of new opto-mechanical data storage devices, allowing information to be written and read by light and stored in the form of molecular vibrations.

̽��ֱ��research is funded as part of a UK Engineering and Physical Sciences Research Council (EPSRC) investment in the Cambridge NanoPhotonics Centre, as well as the European Research Council (ERC) and the Winton Programme for the Physics of Sustainability, and supported by the Spanish Council for Research (CSIC) and the ̽��ֱ�� of the Basque Country (UPV/EHU).

Reference:
Felix Benz et al. ‘Single-molecule optomechanics in ‘pico-cavities’.’ Science (2016). DOI: 10.1126/science.aah5243

Inset image: ̽��ֱ��presence of the sharp metal tip on a plasma sphere concentrates the electric field into its vicinity, initiating a spark. Credit: NanoPhotonics Cambridge

Using the strange properties of tiny particles of gold, researchers have concentrated light down smaller than a single atom, letting them look at individual chemical bonds inside molecules, and opening up new ways to study light and matter.

Single gold atoms behave just like tiny metallic ball bearings in our experiments, with conducting electrons roaming around, which is very different from their quantum life.

Jeremy Baumberg

NanoPhotonics Cambridge/Bart deNijs

Artist's impression

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New state of matter detected in a two-dimensional material

sc604 — Mon, 04 Apr 2016 15:04:40 +0000

An international team of researchers have found evidence of a mysterious new state of matter, first predicted 40 years ago, in a real material. This state, known as a quantum spin liquid, causes electrons – thought to be indivisible building blocks of nature – to break into pieces.

̽��ֱ��researchers, including physicists from the ̽��ֱ�� of Cambridge, measured the first signatures of these fractional particles, known as Majorana fermions, in a two-dimensional material with a structure similar to graphene. Their experimental results successfully matched with one of the main theoretical models for a quantum spin liquid, known as a Kitaev model. ̽��ֱ��results are reported in the journal Nature Materials.

Quantum spin liquids are mysterious states of matter which are thought to be hiding in certain magnetic materials, but had not been conclusively sighted in nature.

̽��ֱ��observation of one of their most intriguing properties — electron splitting, or fractionalisation — in real materials is a breakthrough. ̽��ֱ��resulting Majorana fermions may be used as building blocks of quantum computers, which would be far faster than conventional computers and would be able to perform calculations that could not be done otherwise.

“This is a new quantum state of matter, which has been predicted but hasn’t been seen before,” said Dr Johannes Knolle of Cambridge’s Cavendish Laboratory, one of the paper’s co-authors.

In a typical magnetic material, the electrons each behave like tiny bar magnets. And when a material is cooled to a low enough temperature, the ‘magnets’ will order themselves over long ranges, so that all the north magnetic poles point in the same direction, for example.

But in a material containing a spin liquid state, even if that material is cooled to absolute zero, the bar magnets would not align but form an entangled soup caused by quantum fluctuations.

“Until recently, we didn’t even know what the experimental fingerprints of a quantum spin liquid would look like,” said paper co-author Dr Dmitry Kovrizhin, also from the Theory of Condensed Matter group of the Cavendish Laboratory. “One thing we’ve done in previous work is to ask, if I were performing experiments on a possible quantum spin liquid, what would I observe?”

Knolle and Kovrizhin’s co-authors, led by Dr Arnab Banerjee and Dr Stephen Nagler from Oak Ridge National Laboratory in the US, used neutron scattering techniques to look for experimental evidence of fractionalisation in alpha-ruthenium chloride (α-RuCl₃). ̽��ֱ��researchers tested the magnetic properties of α-RuCl₃ powder by illuminating it with neutrons, and observing the pattern of ripples that the neutrons produced on a screen when they scattered from the sample.

A regular magnet would create distinct sharp lines, but it was a mystery what sort of pattern the Majorana fermions in a quantum spin liquid would make. ̽��ֱ��theoretical prediction of distinct signatures by Knolle and his collaborators in 2014 match well with the broad humps instead of sharp lines which experimentalists observed on the screen, providing for the first time direct evidence of a quantum spin liquid and the fractionalisation of electrons in a two dimensional material.

“This is a new addition to a short list of known quantum states of matter,” said Knolle.

“It’s an important step for our understanding of quantum matter,” said Kovrizhin. “It’s fun to have another new quantum state that we’ve never seen before – it presents us with new possibilities to try new things.”

Reference:
A. Banerjee et al. ‘Proximate Kitaev quantum spin liquid behaviour in a honeycomb magnet.’ Nature Materials (2016). DOI: 10.1038/nmat4604

Researchers have observed the ‘fingerprint’ of a mysterious new quantum state of matter in a two-dimensional material, in which electrons break apart.

It’s an important step for our understanding of quantum matter.

Dmitry Kovrizhin

Genevieve Martin, Oak Ridge National Laboratory

Excitation of a spin liquid on a honeycomb lattice with neutrons.

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Gone in 45 nanoseconds – but a new opportunity for quantum control?

tdk25 — Mon, 22 Dec 2014 04:42:05 +0000

A new study has successfully measured the coherence of electron spin – the period of time in which the particle’s elusive quantum state can be read and manipulated – for an electron trapped in conditions that could form the basis of a future quantum internet.

̽��ֱ��study, reported in the journal Physical Review Letters, was carried out by researchers at the Universities of Cambridge and Saarbrücken. It reveals the coherence time of an electron trapped in a silicon-based colour centre within a microscopic fragment of diamond. This is a gap, manufactured inside the diamond’s lattice structure, and designed to snare an electron so that it can be manipulated.

At just 45 nanoseconds, the time period for which the electron’s spin is visible seems a miniscule fraction, but for scientists trying to bring this under control, it is, in relative terms, an age.

̽��ֱ��“spin” of a particle is its intrinsic angular momentum and can point either up or down. Physicists at numerous leading research universities, including Cambridge, are currently engaged in research which is trying to utilise spin to develop advanced quantum technologies.

In the future, electron spin could be used to represent data and move large amounts of information much faster than is currently possible. This means that better control of spin might well underpin future computing, enable the creation of an entirely new quantum network (or quantum internet), and provide the foundations for a huge range of other technologies, such as advanced sensing devices.

One problem that hinders scientists who are attempting to gain greater command over electron spin for this purpose, however, is that spins in solids cannot be seen, or manipulated, for very long. After a tiny fraction of a second has passed, the spin’s quantum state decays beyond the point of visibility. Therefore, it needs to be retained for long enough for information about the spin to be registered and manipulated.

In the new study, the researchers successfully demonstrated the extent of the coherence of an electron trapped in a “silicon-vacancy” – an impurity in the lattice of carbon atoms that make up diamond. A silicon-vacancy centre provides highly promising conditions for the manipulation of electron spin.

Building on previous research, the researchers put the electron into a “superposition” state, using a technique which involves targeting it with two lasers with carefully-tuned frequencies. In this quantum state, the spin of the electron is potentially both up and down, and it is useful because it provides a basic position from which they can then observe and measure changes using laser pulses. ̽��ֱ��vision for future spin-based technologies involves creating chains of electrons whose spin will change relative to one another based on this initial superposition concept.

When applied to the electron in the silicon vacancy centre, the method achieved a coherence period of tens of nanoseconds – a fraction of time which, for scientists trying to control spin, is actually ample.

Dr Mete Atature, a researcher at the Cavendish Laboratory and St John’s College, ̽��ֱ�� of Cambridge, who led the study with Professor Christoph Becher in Saarbrcüken, said: “This is incremental research, but it essentially deals with the elephant in the room for these colour centres, which was whether there was long-living coherence for the electron spin or not, and whether we had time to see its quantum state?”

“Arguably this is the most pressing challenge for these colour centres right now. We established that we can not only access the electron spin states, but also sustain an arbitrary superposition of them for 45 nanoseconds. When you bear in mind that it will take us picoseconds to execute laser-based operations to manipulate the spin, it becomes clear that just a fraction of this period is required. So this gives us a lot of possibilities to work with.”

̽��ֱ��vacancy centre was created by substituting a silicon atom and a gap in place of two neighbouring carbon atoms in the carbon lattice of a fragment of diamond. Research earlier this year showed that a silicon-based vacancy has the potential to be used for this purpose because the photons – or light particles – emitted by an electron trapped in such conditions are sufficiently bright, and on a sufficiently narrow bandwidth, to be attractive for various applications. ̽��ֱ��research adds to a growing realisation among scientists that silicon-vacancy centres could provide advantageous conditions for spin and photon control, simultaneously.

“Now we know that silicon vacancies provide an alternative colour centre that has spin coherence, optical detectability and superior optical qualities,” Atature added. “ ̽��ֱ��next challenge is to see if we can extend this spin coherence time by various techniques and, in parallel, see if we can entangle the spin with a single photon with sufficiently high fidelity.”

In a breakthrough study scientists have revealed the coherence, or the visibility lifespan, of the spin of an electron in an emerging colour centre in diamond. This could provide a potential component for future quantum networks.

We established that we can not only access the electron spin states, but also sustain an arbitrary superposition of them for 45 nanoseconds. When you bear in mind that it will take us picoseconds to execute laser-based operations to manipulate the spin, it becomes clear that just a fraction of this period is required.

Mete Atature

Atomic structure of the SiV- color center, consisting of an Si impurity (red) situated on an interstitial position along the bond axis and surrounded by a split-vacancy (transparent) and the next-neighbor carbon atoms (grey).

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