Alberto GALINDO (President of the Royal Academy of Sciences)

The irruption of quanta in physics has radically disturbed our view of reality. The relativity demolished the widespread belief in the space and time absoluteness; but one may safely assert that the quantum principles of complementarity and indeterminacy have been more deeply perturbing, as they have obliged us to renounce knowing one half of reality in order to know the complementary half. Moreover, the embodiment of randomness in the quantum formalism, not because of incomplete knowledge, but as an essential imposition of nature, is another feature of the new scientific discourse, implying thereby the abandonment of the Laplacean determinism. Finally, there is an even more intriguing feature of quantum physics: the entanglement. Related to the linear structure of the quantum formalism, the entanglement is responsible, in particular, for the possibility that we might know the state of a compound system while ignoring the states of each of its parties.
Information, seen as memory, processing and communication, is undoubtedly physical. It abides by the physical laws, which give to it their strength and their weakness. The classical information relies on the bits, physical entities which are both robust (under external perturbations) and clonable, and it has a dominant presence in our modern society, which is unimaginable without the support of computers or without the world wide web. But information and quanta met each other about twenty years ago, and from their encounter a promising quantum information has sprung up. Now the dramatis personae are the qubits, fragile and non-clonable. Quantum cryptography and quantum computation outstand as the main research areas in this field.

Article

Advertisements