First the bad news. The entanglement patterns of quantum many-particle systems open up an entirely new world of applications for processing and transmitting information, theoretically in an exponentially much more efficient way than is possible with classical systems. So far so good. But there’s a catch that tempers this optimism: a system of n qubits can only store n classical bits of information. This limitation is also known as the ‘Holevo bound’, named after Alexander Holevo (b. 1943).
