The challenge is that qubits , the building blocks of quantum computers , are very difficult to control . They ’ re highly susceptible to “ noise ” ( interference ), which leads to computational errors . One of the most common breeds of quantum computers is described as being noisy intermediate-scale devices . They ’ re prone to error , and the largest has just over 400 qubits , far from the tens of thousands or even millions that it would take to solve the most complex problems .
Scott Buchholz , global quantum computing lead at Deloitte Consulting LLP , says the noise challenge stems from the difficulty of getting particles like atoms or electrons “ to sit still and then do useful work .” Buchholz compares these particles to 3-year-old toddlers .
“ Toddlers want to talk to everybody , and you ’ re trying to get a whole field of them to sit still and only talk to the right ones in the right way ,” he says . “ All it takes is two toddlers to start squirming , and they all degenerate into a mass of chaos .” And , as you add more toddlers — or particles — the likelihood of chaos grows exponentially .
“ That ’ s analogous to where the quantum space is today , and we need the qubits to grow up and be more mature so we can get them to behave better and work together in the right way ,” Buchholz says .
Another big challenge researchers face is quantum error correction , according to Laflamme . This technique reduces error rates due to noise by encoding a large number of qubits to provide redundancy .
“ Today , technology companies have demonstrated increased control of qubits and ability to scale up , but not enough to do quantum error correction ,” says Laflamme , who has conducted foundational research on error correction . “ To get to quantum error correction , we ’ ll need many tens of thousands of qubits , and what we need to get there is stamina , because
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