Quantum Computer Sets Record For Largest Ever Number of 'Logical Quantum Bits' (newscientist.com) 16
An anonymous reader quotes a report from New Scientist: Another quantum computing record has been broken. A team has built a quantum computer with the largest ever number of so-called logical qubits (quantum bits). Unlike standard qubits, logical qubits are better able to carry out computations unmarred by errors, making the new device a potentially important step towards practical quantum computing. How complicated of a calculation a quantum computer can complete depends on the number of qubits it contains. Recently, IBM and California-based Atom Computing unveiled devices with more than 1000 qubits, nearly tripling the size of previously largest quantum computers. But the existence of these devices has not led to an immediate and dramatic increase in computing capability, because larger quantum computers often also make more errors.
To make a quantum computer that can correct its errors, researchers from the quantum computing start-up QuEra in Boston and several academics focused instead on increasing its number of logical qubits, which are groups of qubits that are connected to each other through quantum entanglement. In conventional computers, error-correction relies on keeping multiple redundant copies of information, but quantum information is fundamentally different and cannot be copied -- so researchers use entanglement to spread it across several qubits, which achieves a similar redundancy, says Dolev Bluvstein at Harvard University in Massachusetts who was part of the team. To make their quantum computer, the researchers started with several thousand rubidium atoms in an airless container. They then used forces from lasers and magnets to cool the atoms to temperatures close to absolute zero where their quantum properties are most prominent. Under these conditions, they could control the atoms' quantum states very precisely by again hitting them with lasers. Accordingly, they first created 280 qubits from the atoms and then went a step further by using another laser pulse to entangle groups of those – for instance 7 qubits at a time -- to make a logical qubit. By doing this, the researchers were able to make as many as 48 logical qubits at one time. This is more than 10 times the number of logical qubits that have ever been created before.
"It's a big deal to have that many logical qubits. A very remarkable result for any quantum computing platform" says Mark Saffman at the University of Wisconsin-Madison. He says that the new quantum computer greatly benefits from being made of atoms that are controlled by light because this kind of control is very efficient. QuEra's computer makes its qubits interact and exchange information by moving them closer to each other inside the computer with optical "tweezers" made of laser beams. In contrast, chip-based quantum computers, like those made by IBM and Google, must use multiple wires to control each qubit. Bluvstein and his colleagues implemented several computer operations, codes and algorithms on the new computer to test the logical qubits' performance. He says that though these tests were more preliminary than the calculations that quantum computers will eventually perform, the team already found that using logical qubits led to fewer errors than seen in quantum computers using physical qubits. The research has been published in the journal Nature.
To make a quantum computer that can correct its errors, researchers from the quantum computing start-up QuEra in Boston and several academics focused instead on increasing its number of logical qubits, which are groups of qubits that are connected to each other through quantum entanglement. In conventional computers, error-correction relies on keeping multiple redundant copies of information, but quantum information is fundamentally different and cannot be copied -- so researchers use entanglement to spread it across several qubits, which achieves a similar redundancy, says Dolev Bluvstein at Harvard University in Massachusetts who was part of the team. To make their quantum computer, the researchers started with several thousand rubidium atoms in an airless container. They then used forces from lasers and magnets to cool the atoms to temperatures close to absolute zero where their quantum properties are most prominent. Under these conditions, they could control the atoms' quantum states very precisely by again hitting them with lasers. Accordingly, they first created 280 qubits from the atoms and then went a step further by using another laser pulse to entangle groups of those – for instance 7 qubits at a time -- to make a logical qubit. By doing this, the researchers were able to make as many as 48 logical qubits at one time. This is more than 10 times the number of logical qubits that have ever been created before.
"It's a big deal to have that many logical qubits. A very remarkable result for any quantum computing platform" says Mark Saffman at the University of Wisconsin-Madison. He says that the new quantum computer greatly benefits from being made of atoms that are controlled by light because this kind of control is very efficient. QuEra's computer makes its qubits interact and exchange information by moving them closer to each other inside the computer with optical "tweezers" made of laser beams. In contrast, chip-based quantum computers, like those made by IBM and Google, must use multiple wires to control each qubit. Bluvstein and his colleagues implemented several computer operations, codes and algorithms on the new computer to test the logical qubits' performance. He says that though these tests were more preliminary than the calculations that quantum computers will eventually perform, the team already found that using logical qubits led to fewer errors than seen in quantum computers using physical qubits. The research has been published in the journal Nature.
so what is the largest number that it has factored (Score:2)
A few hundred digits, most likely.
Re:so what is the largest number that it has facto (Score:4, Interesting)
With 48 logical QBits? Not more than around 5 decimal digits. But it will not have done even that as there are quite a few unsolved problems in making even a QC this small do long and complex calculations.
Re: (Score:2)
> so what is the largest number that it has factored ? A few hundred digits, most likely.
From the summary it's not clear just how functional their machine is. But arglebargle_xiv here just commented on another story the current maximum is 2 digits, i.e. the number 21. - https://science.slashdot.org/c... [slashdot.org]
"After 20-odd years of work on quantum cryptanalysis, the current record from memory is factoring the number 21. That's not a 21-digit or even 21-bit number, it's the product of 3 and 7. However, this hasn
Sooo, 48 logical QBits? (Score:3)
After half a century of research and when, say, breaking current RSA (4096 bits) takes something like 17k logical QBits that must survive a long and complex calculation in an entangled state?
Color me exceptionally unimpressed.
Entanglements (Score:3)
as long as we avoid any "Imperial Entanglements"
Nothing to worry about. (Score:2)
Imperials are classics and therefore do not expose quantum aspects.
Facts Not in Evidence (Score:3)
A helpful reminder that, despite the incredible hype surrounding them, the fundamental promise of quantum computers, the ability to get around pvnp with quantum witchcraft, has never been demonstrated, even theoretically. All this could rather easily turn out to be a dead end. Stories like this are a collusion between tech journalists who need to write lots of stories for little pay, PR firms hired to promote an industry, and start-ups looking to go unicorn by producing enough hype to draw in the big VC dollars. If you put sections of this story into Google, you'll find multiple stories online using the exact same quotes in the exact same order. That's because they were cribbed from a press release and the interviews were done at a junket. Do believe the hype and don't feed into it.
Great! (Score:2)
Great! But can it run Crysis?
Seriously, with these new error-resistant logical qubits they could at least run the Shor's algorithm on a number bigger than 21. The fact that they didn't but preferred to boast the qubits' numbers instead, seems suspicious by itself.
Re: Great! (Score:2)
"physical" vs. "logical" (Score:2)
I mean, are logical qubits not physical, and are physical qubits not logical? Do they mean that the qubit, as a discrete entity, is an emergent property of an underlying complex system (such as a person is, in which case a person is logical but not physical)? But we don't normally use physical/logical as differentiating terms for emergent entities (and now I'm not sure I can think of anything which isn't, somehow, an emergen
Re: (Score:2)
I gather from TFS that they are trying to say that they are entangling multiple physical qubits into a single "logical" qubit in order to get error correction, somehow.
Re: (Score:2)
Coherent for how long? (Score:2)