[ExI] teachers

[BillK]

On Sat, 16 Sept 2023 at 23:51, BillK <pharos at gmail.com> wrote:
>
> On Sat, 16 Sept 2023 at 23:02, efc--- via extropy-chat
> <extropy-chat at lists.extropy.org> wrote:
> >
> > Upon some thought I decided to follow Bills modus operandi of asking
> > iask.ai the following questions about my scenarios below:
> >_______________________________________________
>
>
> Asking these questions to a different AI (there are many nowadays) -
>
> 1. How does a quantum computer store the information in 4000 qubits when
>  there are only 2^260 atoms in the universe?
>
> Quantum computers don't actually store information in physical qubits
> the same way classical bits store 1s and 0s. Instead, the qubits exist
> in superpositions of states that can represent many values
> simultaneously. So 4000 qubits don't need to store 2^4000 distinct
> values - they can explore a space of 2^4000 possibilities in parallel
> during computation. The actual physical implementation only needs to
> maintain the superposition, not store every distinct state. So there
> is no need for an infeasible number of atoms. The power comes from
> manipulating coherences among superpositions to perform computations
> in ways not possible with classical bits. The final read-out then
> samples from the quantum probability distribution to get the result.
>
>
> 2. What is the biggest quantum computer ever built in terms of qubits?
>
> The largest quantum computer built so far in terms of qubits is
> Google's Sycamore processor, which has achieved quantum supremacy with
> 53 qubits. Here are some other notable quantum computers and their
> qubit counts:
>
> IBM quantum computer 'Eagle' - 127 qubits (in 2022)
> IonQ quantum computer - 32 qubits
> Rigetti quantum computer - 40 qubits
> Honeywell quantum computer - 64 qubits
> Quantum Brilliance quantum computer - 19 qubits
> Intel quantum computer 'Horse Ridge' - 49 qubits
> Amazon Braket quantum computer - 32 qubits
>
> So in summary, Google currently holds the record for the largest
> operational quantum computer with 53 qubits in its Sycamore processor.
> IBM is a close second with 127 qubits in their Eagle processor
> unveiled in 2022. But many companies and research labs are working to
> build even larger quantum computers of over 100 qubits and beyond in
> the near future. The race is on to achieve the milestone of quantum
> advantage over classical supercomputers.
>
>
> 3. Are there any limits to how big a quantum computer can be in terms of qubits?
>
> There are both practical and theoretical limits to how large quantum
> computers can scale in terms of number of qubits:
>
> Practical limits:
>
> Noise and decoherence - More qubits means more opportunities for
> errors to creep in from environmental noise, limiting useful
> computation time. Mitigating noise is a huge engineering challenge.
> Connectivity - Connecting many qubits in useful ways for multi-qubit
> gates becomes complex. Current hardware uses nearest-neighbor
> interactions.
> Components - Scaling up requires having many high quality quantum
> processors, amplifiers, cables etc. Very technically challenging.
> Temperature maintenance - Larger systems need more complex cooling
> mechanisms to maintain quantum coherence.
>
> Theoretical limits:
>
> Threshold theorem - To maintain low error rates when correcting
> errors, noise per qubit must be below a threshold to allow
> fault-tolerant quantum error correction.
> Surface code lattice - For 2D surface code error correction, each
> logical qubit may require a lattice of thousands of physical qubits.
> Overheads scale up costs.
> Quantum parallelism - While qubits themselves can represent large
> Hilbert spaces, the number of parallel operations is still limited by
> the number of qubits.
>
> So in practice technical challenges and error rates may prevent a
> quantum computer from exceeding a few hundred well-controlled qubits
> in the near term. But theoretical limits could allow much larger
> computers given low enough physical error rates per qubit. For full
> fault tolerance, millions of physical qubits may be needed per useful
> logical qubit.
>
>
> 4. Is the brain a quantum computer?
>
> No, there is no conclusive evidence that the brain acts as a quantum
> computer. Here are some key reasons why the brain is unlikely to rely
> on meaningful quantum effects:
>
> Temperature - The brain operates at a high temperature, around 310 K.
> Delicate quantum states generally require very low temperatures, near
> absolute zero, to avoid decoherence issues.
> Noise - The noisy, wet environment of the brain would quickly destroy
> most quantum coherence. The brain lacks quantum error correction
> mechanisms.
> Signaling - Neurotransmitter signaling operates classically, without
> evidence of exploiting quantum effects like superposition or
> entanglement.
> Structure - Neurons and synapses are far too large-scale and chaotic
> to support quantum behavior. No atomic-scale qubit architecture
> exists.
> Observation - No quantum effects like interference or tunneling have
> been observed in the brain. Its cognitive functions appear classically
> simulatable.
> Evolution - The brain slowly evolved within a classical environment.
> There are no signs of selective pressures for quantum advantages.
> Consciousness - Reports of quantum effects related to consciousness
> remain speculative and lack robust evidence.
>
> While some small-scale quantum effects may play minor roles in
> biology, overall the brain appears to fully operate via classical
> information processing. There is no evidence that the brain supports
> fundamental quantum computation or that quantum mechanics explains its
> core functions. The search continues for quantum phenomena in the
> brain.
> -----------------------------------------
>
> Interesting different answers?
>
> BillK


I think there might be some confusion re qubits.

Explain logical qubits and physical qubits -

Logical qubits and physical qubits refer to different abstraction
levels when designing and building quantum computers.

Physical qubits are the actual physical implementation of the quantum
bits that store information. They are the hardware the quantum
computer is built from. Examples include superconducting circuits,
trapped ions, and photonics. They have measurable quantum properties
like superposition, entanglement, etc. But they are also prone to
errors and noise.

Logical qubits represent the idealized qubits used in the abstract
quantum circuit model of computation. They are free of noise and
errors. Algorithms are designed using logical qubits, allowing the
programmer to think abstractly about creating superpositions,
interfering alternatives, and getting probabilistic results.

The job of quantum error correction is to encode multiple physical
qubits redundantly to protect the logical qubit state from errors. So
one logical qubit may be represented by 5, 25 or even over 100
physical qubits encoded in a quantum error correcting code.

In simplest terms:

Physical qubits are the noisy hardware components that hold quantum information.
Logical qubits are idealized noiseless qubits that algorithms are designed with.

The coding between the two allows practical physical quantum systems
to emulate the ideal logical qubits required for computation. Bridging
this gap is key to building scalable, fault-tolerant quantum
computers.
-------------------

BillK