**Pp. 54-55:**

Replace:

“But, EPR argued, measurements made on one particle couldn’t instantly affect another particles far away. So, to get around the uncertainty principle, just wait until particles A and B are very far apart, then find the momentum of A. Measuring A’s momentum lets you infer B’s momentum without disturbing B at all. Then simply measure the position of B. Now you know B’s position and momentum, to arbitrary precision, at the same time. Therefore, argued EPR, a particle can have a definite position and momentum at the same time.”

with:

“But, EPR argued, measurements made on one particle couldn’t instantly affect another particle far away. So once particles A and B are very far apart, you can measure A’s momentum, which lets you immediately infer B’s momentum, without affecting B in any way. Or you could measure A’s position instead, which would immediately tell you where B is. You can make either measurement on A—yet crucially, B can’t possibly know which measurement you pick, since it’s so far away from A. So B must have had a definite position and momentum all along, in order to ensure that its properties are in accordance with the outcome of whatever measurement you choose to make on far-distant A.”

(Thanks to David Albert and David Mermin for pointing this out.)

**Pp. 222, 343, 349, 362: **

Replace “Nicholas Gisin” with “Nicolas Gisin”.

**P. 225:**

Replace:

“But Deutsch didn’t actually provide an example of how a quantum computer could outperform a classical one—he had merely proven that it could be done in theory. Finding an algorithm for a computer that hadn’t been built, to outperform all existing ones, was a tall order.”

with:

“But Deutsch didn’t name a practical application where a quantum computer could outperform a classical one—he had just proven that it could be done in theory, and provided a simple example. Finding a useful algorithm for a computer that hadn’t been built, to outperform all existing ones, was a tall order.”

**Pp. 225-226:**

Replace:

“…this difficulty was the basis for nearly all forms of practical cryptography, especially for secure communications over the newly burgeoning Internet. Shor had demonstrated that any kind of secure financial transaction over a computer network—from buying books to trading stocks—would be impossible to accomplish by conventional means in a world with working quantum computers.”

with:

“…this difficulty was the basis for many forms of practical cryptography, especially for secure communications over the newly burgeoning Internet. Shor had demonstrated that the kind of encryption used for nearly all financial transactions over a public computer network—from buying books to trading stocks—would be vulnerable in a world with working quantum computers.”

(Thanks to Ari Rabkin for pointing this out.)