Researchers at the University of New South Wales in Australia have designed a new type of quantum bit (qubit), which they say will enable large-scale quantum
computing at a lower cost. The new ‘flip-flop qubits’ are able to communicate over distances of more than 150nm, which researcher leader Andrea Morello said might
actually leave room to “cram other things between qubits.” What the team have invented is a new way to define a ‘spin qubit’ that uses both the electron and the
nucleus of the atom. Crucially, this new qubit can be controlled using electric signals, instead of magnetic ones,” said Prof Morello.
Morello and his team proposed a method of using both the electron and nucleus of a single phosphorous atom, to create a qubit inside a layer of silicon. ‘Pulling’
the electron away from the nucleus would extend the electric field that qubits use for entanglement. As well as leaving more space, the new chip designs would also
overcome the need for atoms to be very precisely placed.
Even more important, though, is the fact that the new chips could be produced using existing manufacturing technology, which opens up the possibility of mass
production. Morello said that this “makes the building of a quantum computer much more feasible.” “This new idea allows us to fabricate multi-qubit processes with
current technology,” says Guilherme Tosi, the lead scientist.
Australian engineers team from Australia’s University of New South Wales (UNSW) had earlier reported to have created a new quantum bit which remains in a stable
superposition for 10 times longer than previously achieved, dramatically expanding the time during which calculations could be performed in a future silicon quantum
computer. “We have created a new quantum bit where the spin of a single electron is merged together with a strong electromagnetic field,” said Arne Laucht, a
Research Fellow at the School of Electrical Engineering & Telecommunications at UNSW, and lead author of the paper. “This quantum bit is more versatile and more
long-lived than the electron alone, and will allow us to build more reliable quantum computers.”
“The greatest hurdle in using quantum objects for computing is to preserve their delicate superpositions long enough to allow us to perform useful calculations,”
said Andrea Morello, leader of the research team and a Program Manager in the Centre for Quantum Computation & Communication Technology (CQC2T) at UNSW.
“Our decade-long research program had already established the most long-lived quantum bit in the solid state, by encoding quantum information in the spin of a single
phosphorus atom inside a silicon chip, placed in a static magnetic field,” said Andrea Morello. The results are striking: since the electromagnetic field steadily
oscillates at a very high frequency, any noise or disturbance at a different frequency results in a zero net effect. The researchers achieved an improvement by a
factor of 10 in the time span during which a quantum superposition can be preserved.
Specifically, they measured a dephasing time of T2*=2.4 milliseconds – a result that is 10-fold better than the standard qubit, allowing many more operations to be
performed within the time span during which the delicate quantum information is safely preserved. “This new ‘dressed qubit’ can be controlled in a variety of ways
that would be impractical with an ‘undressed qubit’,”, added Morello. “For example, it can be controlled by simply modulating the frequency of the microwave field,
just like in an FM radio. The ‘undressed qubit’ instead requires turning the amplitude of the control fields on and off, like an AM radio.
“In some sense, this is why the dressed qubit is more immune to noise: the quantum information is controlled by the frequency, which is rock-solid, whereas the
amplitude can be more easily affected by external noise”. Since the device is built upon standard silicon technology, this result paves the way to the construction
of powerful and reliable quantum processors based upon the same fabrication process already used for today’s computers. What Laucht and colleagues did was push this
further: “We have now implemented a new way to encode the information: we have subjected the atom to a very strong, continuously oscillating electromagnetic field at
microwave frequencies, and thus we have ‘redefined’ the quantum bit as the orientation of the spin with respect to the microwave field.”
Researchers reported in the journal Nature that they have built a two-qubit logic gate containing two entangled qubits, based on spins of trapped electrons in
silicon for the first time and thereby clearing the hurdle to making silicon-based quantum computer processors a reality.
Such trapped electrons can be integrated with existing CMOS technology, to create quantum computer chips that could store thousands, even millions of qubits on a
single silicon processor chip. UNSW scientists have patented a design for a full-scale quantum chip that would hold millions of silicon qubits.
The UNSW researchers then simulated fundamental gate: the controlled NOT or CNOT operation through their two-qubit logic gate. Depending on the state of the control
qubit, the CNOT gate changes an “up” spin into a “down” spin, and the other way around. The CNOT is the fundamental gate that can be combined to form complex quantum
computations just as NAND gate is fundamental gate in conventional computers.
“For the creation of the two-qubit gate the researchers modified the design of a CMOS transistor. Two gates are placed next to each other on an insulating layer of
silicon dioxide that separates them from a layer of almost pure silicon-28 isotope, writes Alexander Hellemans,” in IEEE spectrum.
Controlling the voltage of the gates allows the trapping of a single electron in the region under the gate. The quantum states of both electrons can be controlled by
gigahertz-frequency pulses transmitted by the “electron spin resonance” (ESR) line, in combination with a 1.4 Tesla magnetic field.
The ESR line allows the spin state for each electron to be set independently for “one-qubit” operations. Voltage pulses entangle the two qubits, allowing them to
operate as a CNOT gate; changing the spin of one electron results in changing the spin of the other electron. The authors write in Nature, “Here we present a
two-qubit logic gate, which uses single spins in isotopically enriched silicon and is realized by performing single- and two-qubit operations in a quantum dot system
using the exchange interaction, as envisaged in the Loss–DiVincenzo proposal.
“We realize CNOT gates via controlled-phase operations combined with single-qubit operations. Direct gate-voltage control provides single-qubit addressability,
together with a switchable exchange interaction that is used in the two-qubit controlled-phase gate. By independently reading out both qubits, we measure clear
anticorrelations in the two-spin probabilities of the CNOT gate.”
Australian scientists design a full-scale architecture for a quantum computer in silicon.
“Our Australian team has developed the world’s best qubits in silicon,” says University of Melbourne Professor Lloyd Hollenberg, Deputy Director of the CQC2T who led
the work with colleague Dr Charles Hill. “However, to scale up to a full operational quantum computer we need more than just many of these qubits – we need to be
able to control and arrange them in such a way that we can correct errors quantum mechanically.”
Australian scientists have designed a 3D silicon chip architecture based on single atom quantum bits, one of the final hurdles to scaling up to an operational
quantum computer many thousands of qubits. Researchers detailed an architecture that sandwiches a 2-D layer of nuclear spin qubits between an upper and lower layer
of control lines. Such triple-layer architecture enables a smaller number of control lines to activate and control many qubits all at the the same time.
By applying voltages to a sub-set of these wires, multiple qubits can be controlled in parallel, performing a series of operations using far fewer controls.
Importantly, with their design, they can perform the 2D surface code error correction protocols in which any computational errors that creep into the calculation can
be corrected faster than they occur.
“This architecture gives us the dense packing and parallel operation essential for scaling up the size of the quantum processor,” says Scientia Professor Sven Rogge,
Head of the UNSW School of Physics. “Ultimately, the structure is scalable to millions of qubits, required for a full-scale quantum processor.”
In theory, the new architecture could pack about 25 million physical qubits within an array that’s 150 micrometers by 150 µm. But those millions of qubits would
require just 10,000 control lines. By comparison, an architecture that tried to control each individual qubit would have required over 1000 times more control lines.
“We have demonstrated we can build devices in silicon at the atomic-scale and have been working towards a full-scale architecture where we can perform error
correction protocols – providing a practical system that can be scaled up to larger numbers of qubits,” says UNSW Scientia Professor Michelle Simmons, study
co-author and Director of the CQC2T.
If the team can pull off this low error rate in a larger system, it would be “quite amazing”, said Hartmut Neven, director of engineering at Google and a member of
the panel. But he cautioned that in terms of performance, the system is far behind others. The team is aiming for ten qubits in five years, but both Google and IBM
are already approaching this with superconducting systems. And in five years, Google plans to have ramped up to hundreds of qubits.
Arrival of Silicon based quantum integrated circuits
Proponents of the silicon technique see major advantages in using a semiconductor to code qubits. They can be manipulated much more simply using microscopic electric
leads etched right onto the chip. And if the same large-scale manufacturing techniques for making chips could be transferred to the quantum realm, it could become
easier to turn the technology into commercial products.
However, integrating CMOS electronics and silicon-based qubits into a single, monolithic chip throw many challenges. In some respects, VLSI technology, thanks to its
focus on minimizing the impact of process variation, guarantees a level of reproducibility that no other industry can provide. However, in the quantum realm,
variability acquires a much higher degree of importance. Even a single atomic-level defect (for example in the quality of the interfaces or the purity and
crystallinity of the material) may lead quantum devices to perform very differently.
Although both technologies can be manufactured using existing silicon industrial processes, these processes currently involve different technological nodes; that is,
they employ slightly different processing standards and protocols at the manufacturing stage. A common “classical-quantum” node will have to be developed and
consolidated to produce hybrid quantum circuits at scale.
Intel Bets It Can Turn Everyday Silicon into Quantum Computing’s Wonder Material
Intel’s silicon qubits represent data in a quantum property called the “spin” of a single electron trapped inside a modified version of the transistors in its
existing commercial chips. “The hope is that if we make the best transistors, then with a few material and design changes we can make the best qubits,” says Clarke.
The design of the spin qubit processors highly resembles the traditional silicon transistor technologies. While there are key scientific and engineering challenges
remaining to scale this technology, Intel has the equipment and infrastructure from decades of fabricating transistors at scale.
The company recently revealed its tiniest quantum chip yet–it’s so small that it can sit comfortably on a pencil eraser. The chip is powered by qubits that are each
more than a thousand times smaller than a single strand of hair. In a typical superconducting quantum computer, qubits live in small loops of superconducting wire
cooled to very low temperatures. Intel’s transistor-free chip relies on a more manageable, readily available, and quintessentially traditional component: silicon.
Some researchers say the retro element that inspired an industry (and a metaphor, a competitive housing market, and a television show) might be key for the next
phase of quantum computing.
PressXAI-UniversityTM was working hard to to make some good progress on the programming side.
The quantum computers are necessary to develop the 6G technology, the hypersonic defences and much more.
A small part of a quantum algorithm to solve the “traveling hypersonic rocket problem”:
(defmacro input-data (&rest data)
(cond ((= (length forms) 1)
`(format *result* "~A ~A~%" ',(car data) ,(car data))
`(format *results* "~A ~A~%" ',forms `(,,@data)))))
(defmacro define-integer-types (&rest bits-)
`(progn
,@(mapcar (lambda (b) `(deftype ,(intern (format nil "UINT~A" b)) () '(unsigned-byte ,b))) bits)
,@(mapcar (lambda (b) `(deftype ,(intern (format nil "INT~A" b)) () '(signed-byte ,b))) bits)))
Quantum Entanglement - a new perspective
PressXAI-Cyber Security
DNA analysis
Similarly to the mRNA which is a "software of life" - we work on solutions, which are the mRNA for the software.
This leads to a self-learning computer programs, where the code is reprogramming itself.
It is different than the machine-learning, which helps to discover the results.
The PressXAI-MindTM discovers itself.
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