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All the memory circuits I've seen use some form of flip-flop/feedback mechanism to store a value. Is this the only circuit design that can store a value? Is there anyway to create memory without a feedback loop?

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Flash memory stores bits in an isolated conductor within a floating gate transistor, with no feedback required to maintain the state.

DRAM stores data in the charge state of a capacitor, however the data will be lost over time due to leakage currents.

Core memory can store a bit in the magnetic state of a magnetic material. Feedback isn't required to maintain the state, but it can only be read once before the state is disturbed.

Fuses can be used to store information by simply overheating and destroying a small wire (or not). The state is maintained without feedback. However, they can only be written once.

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    \$\begingroup\$ As an extension of core memory, hard disks and floppy disks are also not flip-flops (otherwise they'd be called flip-floppy disks!). Also any number of weird old memory technologies out there like bubble memory, delay-line memory, and probably more. And some new ones, like MRAM and FRAM. \$\endgroup\$ – Hearth Nov 28 '18 at 3:04
  • \$\begingroup\$ @KingDuken, and punch cards. \$\endgroup\$ – The Photon Nov 28 '18 at 3:09
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To add to this list:

Optical Drives that encodes binary data. There is a laser that reads reflections on a particular surface. If there is no reflection of that bit, there is a zero. Otherwise, if there is a reflection of that bit, there is a one. The data that is stored is in the form of Gray Code.

Punch cards, now considered rather obsolete, actually contains digital data. Each hole, or lack thereof, would represent actual code for a computer to execute. This website gives an example of how hole punches can relate to real code.

Writing is, while not relevant to this website, probably the oldest form of external memory outside of the living organism.

I suppose you can say the oldest form of memory is a nucleoid in a prokaryotic cell since that stores information on how it operates...

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  • \$\begingroup\$ Quantum computing has nothing to do with supersymmetry. Supersymmetry isn't even part of our current understanding of quantum mechanics, and there seems to be some evidence pointing to it not existing, at least at the energy scales considered most likely. \$\endgroup\$ – Hearth Nov 28 '18 at 4:03
  • \$\begingroup\$ @Felthry Deleted lol. Shows you how little I know about the topic :) \$\endgroup\$ – KingDuken Nov 28 '18 at 4:04
  • \$\begingroup\$ I think you might have meant superposition, which is closer to correct but still not quite. \$\endgroup\$ – Hearth Nov 28 '18 at 4:05
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Assuming by memory you mean digital synchronous, the answer is YES. The simplest FF is the fundamental sync memory cell which has internal feedback.

The async latch has external feedback using 2 gates.

By asynchronous memory, NO , it can be an isolated charge with a transmission gate or similar transistor type.

But be more explicit next time. Your question indicates a opportunity to expand your awareness.

. Do you assume we know you mean only voltatile static RAM or all types of memory:

analog/digital, static/dynamic , electrical/mechanical/magnetic/optical/nuclear/acoustic or chemical

. Each type has a threshold, which is not necessarily binary but I assume you mean logical and not visual , it can be linear or not, but must have defined thresholds and tolerances.

The question of "memory without a FF and/or feedback?" ... Could be simply Yes.

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