Can Wiesner's quantum money be realized (with logical qubits) today?

Question

Consider Wiesner's quantum money scheme. With today's devices and today's error correction and mitigation schemes, how long can we hold $n$ logical qubits such that they are all (logically) in a product state, with each logical qubit being drawn uniformly at random from one of the BB84 states $\{|0\rangle_L,|1\rangle_L,|+\rangle_L,|-\rangle_L\}$, say, for $n=10$ or $20$ or $30?$

In Wiesner's scheme:

1. We don't need to act fault-tolerantly on the logical qubits, as there's no two-qubit computation being done on the logical qubits in Wiesner's scheme;
2. In particular each qubit is prepared and measured in one of the four BB84 basis states - thus assuming easy preparation of $|0\rangle_L$, the only relevant logical single-qubit gates are the Hadamard and the X/NOT gate (no arbitrary phases or T gates are needed); and
3. Because one whole bill can be written as a product state over all logical qubits, indeed, I can imagine that the $n$ qubits in a bill are prepared and distributed over multiple processors - one processor holding one (logical) qubit, another holding another, etc.

Answer 1

Today's logical memories are not good enough yet to realize Wiesner's quantum money scheme. Take a look at the screenshot below, taken from a recording of Shraddha Singh's QIP 2023 talk on Real-time quantum error correction beyond break-even. It shows the difference between the lifetime of a logical qubit (logical lifetime) and a bare, unencoded qubit (best physical lifetime). A red arrow indicates that the lifetime of the logical qubit is shorter(!) than the lifetime of a physical qubit. A green arrow indicates an increase in lifetime. There are two green arrows, but they are way too short.