[HN Gopher] IBM releases first-ever 1k-qubit quantum chip
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       IBM releases first-ever 1k-qubit quantum chip
        
       Author : birriel
       Score  : 25 points
       Date   : 2023-12-04 18:12 UTC (4 hours ago)
        
 (HTM) web link (www.nature.com)
 (TXT) w3m dump (www.nature.com)
        
       | vlovich123 wrote:
       | The number of qbits reported needs to be the logical and physical
       | number. If I'm reading it right, this chip has 1 logical qbit? Is
       | this a record? Or is it 10 logical qbits and that's the record?
       | 
       | > Researchers have generally said that state-of-the-art error-
       | correction techniques will require more than 1,000 physical
       | qubits for each logical qubit. A machine that can do useful
       | computations would then need to have millions of physical qubits.
       | 
       | > But in recent months, physicists have grown excited about an
       | alternative error-correction scheme called quantum low-density
       | parity check (qLDPC). It promises to cut that number by a factor
       | of 10 or more, according to a preprint by IBM researchers
        
         | da-bacon wrote:
         | This chip has 0 logical qubits, for any reasonable definition
         | of logical qubit: it's not good enough (yet) to offer
         | substantial error suppression by using a quantum error
         | correcting code. (Disclosure: work for Google's quantum effort)
        
           | vlovich123 wrote:
           | Since you probably know, has anyone managed to create a
           | logical qbit yet?
        
             | da-bacon wrote:
             | Yes, for some definition of logical qubit.
             | 
             | One of the first example is the experiment of Egan et al
             | where they demonstrated a fault-tolerant QEC measurement
             | using 13 physical qubits. https://arxiv.org/abs/2009.11482
             | They show improvements in the logical performance on the
             | codes, but it is still a pretty small improvement (factor
             | of 2).
             | 
             | Another example is the experiment we performed at Google
             | https://arxiv.org/abs/2207.06431 where we used
             | superconducting qubits. In that experiment we showed that
             | we were able to go from a small code to a slightly larger
             | code and that the error got "slightly better" as you scaled
             | things up.
             | 
             | Other groups have also demo-ed small scale logical qubits.
             | Notable ones include those done by Quantinuum (trapped ion
             | qubits) and ETH Zurich (superconducting qubits). But all of
             | these show very small improvements in error rates. To truly
             | build "logical" qubits one would hope to get suppression of
             | errors by factors of like 100-1000, and no one is really
             | close to that right now.
        
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       (page generated 2023-12-04 23:02 UTC)