QR codes have become a convenience of modern life. Just scan the black and white mosaic with your phone’s camera and you can do everything from connect to your hotel room Wi-Fi to pay for that public ...

For those of us who weren't paying attention, over the last few years, scientists around the world have been one-upping each other in a bid to create the smallest QR code that can be reliably read.

In a hotel lobby, two QR Codes promote the same thing: a 10% discount on the breakfast buffet. One sits at eye level beside the elevator buttons, right where guests wait with their phones in hand. The ...