Set backend parameters
Depending on the backend, some settings affecting the backend's noise characteristics can be configured.
Available parameters
Summary
Model | average_nb_photons | kappa_1 | kappa_2 | distance | Availability |
---|---|---|---|---|---|
QPU:1Q:BOSON_4A | ✅ | ❌ | ❌ | ❌ | Remote only |
QPU:1Q:BOSON_4B | ✅ | ❌ | ❌ | ❌ | Remote only |
QPU:1Q:BOSON_4C | ✅ | ❌ | ❌ | ❌ | Remote only |
EMU:1Q:LESCANNE_2020 | ✅ | ❌ | ❌ | ❌ | Remote & Local |
EMU:6Q:PHYSICAL_CATS | ✅ | ✅ | ✅ | ❌ | Remote & Local |
EMU:40Q:PHYSICAL_CATS | ✅ | ✅ | ✅ | ❌ | Remote & Local |
EMU:15Q:LOGICAL_EARLY | ✅ | ✅ | ✅ | ✅ | Remote & Local |
EMU:40Q:LOGICAL_TARGET | ✅ | ✅ | ✅ | ✅ | Remote & Local |
Average number of photons
average_nb_photons
is the number photons trapped in the qubit’s cavity.- Increasing it will exponentially decrease the number of bit-flips, at the cost of a linear increase of the number of phase-flips.
- This parameter is available in all backends.
\(\kappa_1\) and \(\kappa_2\)
\(\kappa_1\)
kappa_1
is the one-photon loss rate, expressed in Hz.- Qubit quality decreases as
kappa_1
increases, since one-photon losses causes phase-flips. - Boson 4 chips feature
kappa_1 = 3.14*19_900
. - This parameter is not available on a real chip and on digital twin emulators.
\(\kappa_2\)
kappa_2
is the two photon-loss rate, expressed in Hz.- Qubit quality increases as
kappa_2
increases, since the exchange of pairs of photons is used to stabilize the qubit. - Boson 4 chips feature
kappa_2 = 3.14*250_000
. - This parameter is not available on a real chip and on digital twin emulators.
\(\kappa_1/\kappa_2\)
- The \(\kappa_1/\kappa_2\) ratio is a good proxy for the quality of the physical chip.
- The lower this ratio, the higher the quality of the chip.
- Current Alice & Bob chips feature \(\kappa_1/\kappa_2 < 10^{-2}\)
- Getting error correction to work reliably requires \(\kappa_1/\kappa_2 < 10^{-3}\)
- Creating 100 logical qubits at a \(10^{-8}\) error rate with 1500 qubits requires \(\kappa_1/\kappa_2 < 10^{-4}\), as shown in this article
- Running Shor's algorithm on a 2048-bit number requires \(\kappa_1/\kappa_2 < 10^{-5}\), as shown in this article
Repetition code distance
distance
is the distance of the error correction code, i.e. the number of physical qubits used to create a logical qubits.- Phase-flips are exponentially removed as the distance of the code is increased, but bit-flips increase linearly.
- This parameter is only available for logical backends.
Set parameters
Parameters may be set while initializing a backend:
from qiskit_alice_bob_provider import AliceBobLocalProvider
from qiskit import QuantumCircuit, execute
provider = AliceBobLocalProvider()
backend = local.get_backend('EMU:1Q:LESCANNE_2020', average_nb_photons=3)
backend = local.get_backend('EMU:6Q:PHYSICAL_CATS', average_nb_photons=5)
backend = local.get_backend('EMU:40Q:PHYSICAL_CATS', kappa_2=500_000)
backend = local.get_backend('EMU:15Q:LOGICAL_EARLY', distance=13)
circuit = QuantumCircuit(...)
# ...
execute(circuit, backend, shots=3000)
Or when executing a circuit:
from qiskit_alice_bob_provider import AliceBobRemoteProvider
from qiskit import QuantumCircuit, execute
# Replace the placeholder with your actual API key in the line below
remote = AliceBobRemoteProvider(api_key='YOUR_API_KEY')
backend = remote.get_backend('EMU:1Q:LESCANNE_2020')
circuit = QuantumCircuit(...)
# ...
execute(circuit, backend, shots=3000, average_nb_photons=3)