sentence1: in their seminal work , knill , laflamme , and milburn showed that such a quantum processor could be constructed using only linear optical elements , at the expense of rendering each quantum logic gate probabilistic .
sentence2: indeed , in an influential paper , knill , laflamme , and milburn showed that the exponential speed-up over a classical algorithm afforded by quantum mechanics can be reached using only linear optics with single-photon detectors .