ELI5: why is quantum computing hard

Quantum computing is hard because quantum bits (qubits) are super delicate and hard to control, unlike regular bits in your computer.

Imagine you have a light switch (bit) that can only be either on (1) or off (0). That's easy to understand! Now, imagine a special dimmer switch (qubit) that can be both on and off at the same time, or somewhere in between! This "both at once" state is called superposition.

• This dimmer switch is super sensitive. Even a little bit of noise, like someone talking loudly or a tiny vibration, can make it jump to being either fully on or fully off, losing the "both at once" state. This noise is called decoherence.

• Think of it like trying to balance a pencil perfectly on its tip. Easy to do for a second, right? But any tiny breeze or wobble will make it fall. Qubits are like that pencil – very easily disturbed.

• Also, imagine you have a bunch of these dimmer switches that need to work together in a very specific way (entanglement). If even one switch gets messed up, the whole group of switches can fail.

• Keeping qubits in a stable "both at once" state is incredibly difficult.
• Making lots of qubits work together (entanglement) without disturbing them is even harder.
• We need to build special, super-cooled environments to protect the qubits from noise.