A quantum computer (also known as a quantum supercomputer) is a computation device that makes direct use of quantum-mechanical phenomena, such as superposition and entanglement, to perform operations on data. Quantum computers are different from digital computers based on transistors. Whereas digital computers require data to be encoded into binary digits (bits), quantum computation uses quantum properties to represent data and perform operations on these data.
NSA is reported to be developing this computing hardware for its clandestine code-breaking mission. According to a report published in The Washington Post, with such technology at NSA’s disposal, all current forms of public key encryption would be broken, including those used on many secure Web sites as well as the type used to protect state secrets. The documents provided by Snowden suggest that the NSA is no closer to success than others in the scientific community. Report also states that NSA is running neck-to-neck with quantum computing labs sponsored by the European Union and the Swiss government, with steady progress but little prospect of an immediate breakthrough.
The documents, however, indicate that the agency carries out some of its research in large, shielded rooms known as Faraday cages, which are designed to prevent electromagnetic energy from coming in or out. Those, according to one brief description, are required “to keep delicate quantum computing experiments running.”
Quantum Computer basics and challenges in its developments :
A quantum computer maintains a sequence of qubits. A single qubit can represent a one, a zero, or any quantum superposition of these two qubit states; moreover, a pair of qubits can be in any quantum superposition of 4 states, and three qubits in any superposition of 8. In general, a quantum computer withn qubits can be in an arbitrary superposition of up to 2 power n different states simultaneously (this compares to a normal computer that can only be in one of these 2 power n states at any one time). A quantum computer operates by setting the qubits in a controlled initial state that represents the problem at hand and by manipulating those qubits with a fixed sequence of quantum logic gates. The sequence of gates to be applied is called a quantum algorithm. The calculation ends with measurement of all the states, collapsing each qubit into one of the two pure states, so the outcome can be at most n classical bits of information.
While a classical computer, however fast, must do one calculation at a time, a quantum computer can sometimes avoid having to make calculations that are unnecessary to solving a problem. That allows it to home in on the correct answer much more quickly and efficiently. Quantum computing is difficult to attain because of the fragile nature of such computers. In theory, the building blocks of such a computer might include individual atoms, photons or electrons. To maintain the quantum nature of the computer, these particles would need to be carefully isolated from their external environments. Integer factorization is believed to be computationally infeasible with an ordinary computer for large integers if they are the product of few prime numbers (e.g., products of two 300-digit primes). By comparison, a quantum computer could efficiently solve this problem using Shor’s algorithm to find its factors. This ability would allow a quantum computer to decrypt many of the cryptographic systems in use today, in the sense that there would be a polynomial time (in the number of digits of the integer) algorithm for solving the problem. In particular, most of the popular public key ciphers like RSA are based on the difficulty of factoring integers (or the related discrete logarithm problem, which can also be solved by Shor’s algorithm). These are used to protect secure Web pages, encrypted email, and many other types of data. Breaking these would have significant ramifications for electronic privacy and security.
Report further added that –Experts think that one of the largest hurdles to breaking encryption with a quantum computer is building a computer with enough qubits, which is difficult given the very fragile state of quantum computers. By the end of September, the NSA expected to be able to have some building blocks, which it described in a document as “dynamical decoupling and complete quantum control on two semiconductor qubits.”
Reference : Wikipedia
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