IBM is investing $3 Billion dollars over the next five years to explore and develop computers that mimic human brain functions: a cognitive computer.

Carbon nanotubes, which are cylinders made of carbon atoms, show the most promise as a silicon replacement. IBM researchers are shrinking the size of carbon nanotubes, but challenges remain in cooling them down and there is considerable debate around safety concerns. However, there is consensus that technical problems could be solved, Guha said.

Brain and quantum computers also involve research on computer behavior.

IBM is developing computers that mimic brain-like functionality as part of its Synapse program. The computer makes an approximation of how the brain processes information in parallel via trillions of connections, which are the synapses. IBM in 2011 demonstrated a neural chip with programmable and learning synapses that have navigation and pattern recognition abilities. IBM's goal is to build a neural chip that mimics the human brain, with 10 billion neurons and 100 trillion synapses but that uses just 1 kilowatt of power.

At the heart of quantum computers are quantum bits (qubits), which hold values of 1 and 0, which are unlike bits in conventional computers that are at a state of 1 or 0 at any given time. By storing and sharing data in more states, the qubits could speed up calculations.