The challenges of quantum computing

Subject : Science and Technology

Context:

In 2021 the Indian government launched a National Mission to study quantum technologies with an allocation of ₹8,000 crores; the army opened a quantum research facility in Madhya Pradesh, and the Department of Science and Technology co-launched another facility in Pune.

Quantum computer (QC):

Quantum computers mimic the behaviour of atoms and subatomic particles to drastically increase processing speed.
The qubit is the fundamental unit of a Quantum Computer (QC).
These particles can exist in several states simultaneously, a puzzling phenomenon called quantum superposition.
- In Quantum superposition, quantum objects form inextricable bonds, or entangle, with one another and influence each other’s behaviours, even from large distances.
- Two or more bonded quantum objects create a delicate ecosystem called a composite quantum system.
- This means that if one object in the system is disturbed, every object with which it is entangled will also be disturbed.

How does a computer use quantum superposition?

The bit is the fundamental unit of a classical computer.
- Its value is 1 if a corresponding transistor is on and 0 if the transistor is off.
- The transistor can be in one of two states at a time – on or off – so a bit can have one of two values at a time, 0 or 1.
In the Qubits, instead of being either 1 or 0, the information is encoded in a superposition: say, 45% 0 plus 55% 1.
This is entirely unlike the two separate states of 0 and 1 and is the third kind of state.
One qubit can encode two states. Five qubits can encode 32 states. A computer with N qubits can encode 2N states – whereas a computer with N transistors can only encode 2 × N states.
So a qubit-based computer can access more states than a transistor-based computer, and thus access more computational pathways and solutions to more complex problems.
It’s typically a particle like an electron.

What are Transmons:

In quantum computing, and more specifically in superconducting quantum computing, a transmon is a type of superconducting charge qubit that was designed to have reduced sensitivity to charge noise.
Google and IBM have been known to use transmons, where pairs of bound electrons oscillate between two superconductors to designate the two states.

Challenges in their practical usage:

Researchers face some fractious challenges.
A practical QC needs at least 1,000 qubits. The current biggest quantum processor has 433 qubits.
There are no theoretical limits on larger processors; the barrier is engineering-related.
Qubits exist in superposition in specific conditions, including very low temperatures (~0.01 K), with radiation shielding and protection against physical shock. Even a minuscule shock can collapse the quantum state, a phenomenon called decoherence.
Material or electromagnetic defects in the circuitry between qubits could also ‘corrupt’ their states and bias the eventual result.
Researchers are yet to build QCs that completely eliminate these disturbances in systems with a few dozen qubits.
Error correction is also tricky. The no-cloning theorem states that it’s impossible to perfectly clone the states of a qubit.

Opportunities:

Quantum has the potential to significantly increase the connectivity, security, and speed of the internet.
The so-called quantum internet links quantum devices together using entanglement.
It can provide a hack-free communication system using quantum cryptography.