Efficient quantum error correction in neutral atoms by conversion to erasure errors
View Patent ↗A method for quantum error correction includes: trapping and/or manipulating an array of qubits that include encoded neutral atoms or ions and forms a computational space; encoding the array of qubits to a state characterized in that an error during at least one of an idling, gate, or other operation results in a respective qubit transition to a disjointed state where that error can be detected without disturbing the qubits remaining in the computational space; performing a syndrome measurement of a quantum error correcting code; identifying the presence and location of an error by detecting the corresponding neutral atom or ion has left the computational space after performing the operation; identifying a logical error in the quantum error correcting code associated with a loss of qubit information based on the identified error location and results of the syndrome measurement; and adjusting subsequent computational steps based on the identified logical error.
1 . A system for quantum error correction, comprising:
a quantum system comprising an array of qubits;
an optical system configured to trap, manipulate, and/or detect the array of qubits using light;
a processor; and
a memory, including instructions stored thereon, which when executed by the processor, cause the quantum system to:
trap and/or manipulate the array of qubits by the optical system, wherein the array of qubits includes encoded neutral atoms or ions and forms a computational space;
encode each qubit in the array of qubits to a state characterized in that an error during at least one operation including idling, a gate, or other operation, results in a respective qubit transition to a disjointed state where that error can be detected without disturbing the qubits remaining in the computational space, wherein the array of qubits form a quantum error correcting code and the detected error comprises an erasure error;
perform a syndrome measurement of a quantum error correcting code;
identify a presence and location of an error by detecting that the corresponding neutral atom or ion has left the computational space after performing the at least one operation;
identify a logical error in the quantum error correcting code associated with a loss of qubit information based on the identified error location and results of the syndrome measurement; and
adjust subsequent computational steps based on the identified logical error.
2 . The quantum system of claim 1 , wherein adjusting subsequent computational steps includes at least one of fixing the error or rejecting the results of a portion of the computation and repeating the portion of the computation.
3 . The quantum system of claim 1 , wherein for the gate operation the instructions when executed by the processor further cause the quantum system to:
process the qubits in accordance with the gate operation, wherein the gate operation is performed by optical coupling of qubits to an excited state;
detect the error by detecting that the corresponding neutral atom or ion has left the computational space after performing the gate operation;
identify the location or a time of the detected error; and
replace or reinitialize an atom or an ion of a qubit associated with the detected error.
4 . The quantum system of claim 1 , wherein during idling or a gate operation, errors may be caused by Raman or Rayleigh scattering, or spontaneous decay, which results in a transition outside of the computational space.
5 . The quantum system of claim 4 , wherein the instructions when executed by the processor, further cause the quantum system to:
optically pump metastable states other than computational states to a ground state to facilitate detection while avoiding transitions into the computational space.
6 . The quantum system of claim 5 , where population in the ground states is detected using cycling fluorescence on a transition that does not disturb the computational space.
7 . The quantum system of claim 3 , wherein during a gate operation, wherein the excited state comprises a highly excited Rydberg state and errors may be caused by thermal photons via absorption or simulated emission while in the excited state, which results in a transition outside of the computational space.
8 . The quantum system of claim 7 , wherein the instructions when executed by the processor, further cause the quantum system to:
directly detect a population remaining in Rydberg states at an end of each gate operation without performing error syndrome measurements with ancilla qubits.
9 . The quantum system of claim 7 , wherein the detection is performed by:
optically pumping metastable states other than computational states to a ground state to facilitate detection while avoiding transitions into the computational space.
10 . The quantum system of claim 9 , wherein the detection is further performed by:
detecting atoms in trapped Rydberg states by waiting for the atoms to decay to the ground state and detecting cycling fluorescence from the ground state.
11 . The quantum system of claim 7 , wherein the detection is performed by:
detecting atoms remaining in Rydberg states by ionizing them using an autoionizing excitation on a core electron and then detecting cycling fluorescence from the same transition in the ion.
12 . The quantum system of claim 7 , wherein the detection is performed by:
detecting atoms remaining in Rydberg states by ionizing them using an autoionizing excitation and detecting ions directly with an ion detector and ion optics.
13 . The quantum system of claim 1 , wherein the instructions when executed by the processor, further cause the quantum system to:
encode a qubit in metastable electronic states, wherein a transition outside of those states are indicative of an error.
14 . The quantum system of claim 13 , wherein the qubits comprise 171-ytterbium atoms, and the encoding states comprise hyperfine states of a 6s6p 3 P 0 F=1/2 level in 171 Yb.
15 . The system of claim 1 , wherein transitions outside of the computational space are detected by measuring a 6s 2 1 S 0 ground state population, using cycling fluorescence on the 6s 2 1 S 0 ->6s6p 1 P 1 transition with a wavelength near 399 nm, which does not disturb atoms remaining in the computational space.
16 . The quantum system of claim 7 , wherein the highly excited Rydberg state comprises a state belonging to a 6sns 3 S 1 F=3/2 Rydberg level with principal quantum number n substantially within a range of 40-100.
17 . The quantum system of claim 7 , wherein the highly excited Rydberg state includes Rydberg levels with a Rydberg electron having orbital angular momentum L=0, L=1 or L=2, and principal quantum number substantially within a range of 40-100, and a total angular momentum F=1/2, 3/2, or 5/2.
18 . The system of claim 7 , wherein a population remaining in Rydberg states at an end of the gate is converted into Yb + ions by driving a 6s 1/2 ->6p 1/2 inner electron transition near 369 nm, resulting in autoionization.
19 . The system of claim 7 , wherein Yb + ions are detected using cycling fluorescence on the Yb + ion 6s 1/2 ->6p 1/2 transition with a wavelength near 369 nm, which does not disturb ions remaining in the computational space.
20 . The quantum system of claim 1 , wherein the instructions when executed by the processor, further cause the quantum system to:
replace, using an optical tweezer, each neutral atom or ion that has left the computational space with a replacement neutral atom or ion having a predefined state.
21 . A method for quantum error correction, comprising:
trapping and/or manipulating an array of qubits, wherein the array of qubits includes encoded neutral atoms or ions and forms a computational space;
encoding the array of qubits to a state characterized in that an error during at least one operation including idling, a gate, or other operation results in a respective qubit transition to a disjointed state where that error can be detected without disturbing the qubits remaining in the computational space, wherein the array of qubits form a quantum error correcting code and the detected error comprises an erasure error;
performing a syndrome measurement of a quantum error correcting code;
identifying the presence and location of an error by detecting the corresponding neutral atom or ion has left the computational space after performing the at least one operation;
identifying a logical error in the quantum error correcting code associated with a loss of qubit information based on the identified error location and results of the syndrome measurement; and
adjusting subsequent computational steps based on the identified logical error.
22 . A quantum system for quantum error correction, comprising:
an optical system configured to trap, manipulate, and/or detect an array of qubits using light;
a processor; and
a memory, including instruction stored thereon, which when executed by the processor, cause the quantum system to:
trap and/or manipulate the array of qubits, wherein the array of qubits includes encoded neutral atoms or ions and forms a computational space;
encode the array of qubits to a state characterized in that an error during at least one of an idling, gate, or other operation results in a respective qubit transition to a disjointed state where that error can be detected without disturbing the qubits remaining in the computational space;
for each gate operation detect an erasure error and replace or reinitialize an atom or an ion of a qubit associated with the detected erasure error;
identify an error location within the quantum error correcting code based on the detected error;
identify a logical error in the quantum error correcting code associated with a loss of qubit information based on the identified error location; and
adjust the subsequent computational steps to correct the error.