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## error-correcting the IBM qubit panos aliferis IBM the IBM qubit – three Josephso

DeJesus, Ed, Contributing Writer has reference to this Academic Journal, PHwiki organized this Journal error-correcting the IBM qubit panos aliferis IBM the IBM qubit – three Josephson junctions – three loops – high-Q superconducting transmission line – three Josephson junctions – three loops – high-Q superconducting transmission line – three side transmission lines as long as – two SQUIDs as long as measurement flux control – Q~104 ( but 106 @ 4K possible) – T1~3s @ IBM – T1~15ns @ IBM ( but ~s elsewhere) the IBM qubit

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parameter space 1) flux difference in two big loops, 2) control flux, (mostly in small loop) as long as , symmetry adjusts the potential barrier – three Josephson junctions – three loops – high-Q superconducting transmission line – three side transmission lines as long as – two SQUIDs as long as measurement flux control – Q~104 ( but 106 @ 4K possible) – T1~3s @ IBM – T1~15ns @ IBM ( but ~s elsewhere) the IBM qubit the IBM qubit basis as long as persistent currents the IBM qubit

the problem – in arXiv:0709.1478, the IBM team, Brito , DiVincenzo, Koch, in addition to Steffen , discussed pulsed gates as long as their qubit. – they estimated gate fidelities of the order of 99%, in addition to they observed noise is biased with bias ~10. so, Panos, are we below threshold as long as most qubits, . the problem – in fact, dephasing is much stronger than de-excitation in many systems the obvious question is, can we exploit this noise asymmetry to improve the threshold as long as quantum computation – they estimated gate fidelities of the order of 99%, in addition to they observed noise is biased with bias ~10. – in arXiv:0709.1478, the IBM team, Brito , DiVincenzo, Koch, in addition to Steffen , discussed pulsed gates as long as their qubit. so, Panos, are we below threshold the problem – but this is tricky. why 1) the gates that we apply can destroy this asymmetry; e.g., Hadamard gates will propagate errors to errors.

the problem – but this is tricky. why 1) the gates that we apply can destroy this asymmetry; e.g., Hadamard gates will propagate errors to errors. 2) in addition to even if we restrict to gates that propagate phase errors to phase errors alonee.g., the CNOT, noise in the gates may not be biased; e.g., to describe noise in a CNOT, you need operators that contain . the problem – but this is tricky. why 1) the gates that we apply can destroy this asymmetry; e.g., Hadamard gates will propagate errors to errors. 2) in addition to even if we restrict to gates that propagate phase errors to phase errors alonee.g., the CNOT, noise in the gates may not be biased; e.g., to describe noise in a CNOT, you need operators that contain . 3) in addition to even if we restrict to diagonal gates to avoid (1) & (2), errors can propage to errors via measurements; e.g., think of teleportation in addition to cluster- state computation. the idea – our quantum computer will execute biased noise more balanced effective noise with str. below effective noise with arbitrarily small str. – we will encode the ideal quantum circuit by using . concatenated CSS code length-n repetition code where

the idea – our quantum computer will execute – but, how biased is noise as long as operations in biased noise more balanced effective noise with str. below effective noise with arbitrarily small str. – we will encode the ideal quantum circuit by using . concatenated CSS code length-n repetition code mostly operate here; the S line the IBM qubit qubit parked – resting qubits are parked the IBM qubit

qubit parked measurement point – resting qubits are parked – to measure, we completely unpark in addition to move to flux-qubit region the IBM qubit qubit parked measurement point portal – as long as diagonal one-qubit gates, we unpark, approach the portal, in addition to park again – resting qubits are parked – to measure, we completely unpark in addition to move to flux-qubit region the IBM qubit always on the IBM qubit

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estimates we will only use this set estimates we will only use this set – indirect implementations use 3 CPHASE gates, or 1 CPHASE in addition to 2 Hadamards. estimates we will only use this set – indirect implementations use 3 CPHASE gates, or 1 CPHASE in addition to 2 Hadamards.

estimates we will only use this set – indirect implementations use 3 CPHASE gates, or 1 CPHASE in addition to 2 Hadamards. the scheme the problem with leakage

the problem with leakage the problem with leakage – if a qubit leaks, then leakage can propagate (with probability ~10-3) to every other qubit that interacts with it. – although this is a rare effect, it is useful to have a simple way to block leakage from spreading. the problem with leakage repeat – in addition to now note that there is no way as long as a single leakage error to propagate to both output blocks.

comments – by taking to be the concatenated 4-qubit code, in addition to using a Fibonacci decoding scheme, we find our error rates are below threshold (we can use the 3-bit repetition code, in addition to 3 measurement repetitions.) NEY 1) our analysis shows we are just below thresholdoverhead is large, 2) the scheme is not geometrically local, 3) we have assumed noise is described by superoperatorsno memory. – should we celebrate ! – The message as long as experiments is that CPHASE can effectively replace the CNOT, in addition to that the more biased the noise the more useful the qubit. YEY 1) our analysis is rigorous but not tightbelieving Knill, we may be significantly below threshold, in addition to the overhead will be moderate, 2) we use very small codes, so the penalty as long as en as long as cing locality may only be a small factor, 3) since 1/f noise is primarily due to bath spins in the proximity of each qubit, correlated errors will mainly occur on already erroneous qubits. threshold theorem & level reduction PA, Gottesman, in addition to Preskill, quant-ph/0504218, Knill, quant-ph/0410199 & references & my thesis, quant-ph/0703230 PA, quant-ph/0709:3603 Fibonacci scheme quantum computing against biased noise PA in addition to Preskill, arXiv:0710.1301 PA, Brito, DiVincenzo, Steffen, Preskill, in addition to Terhal; soon.

## DeJesus, Ed Contributing Writer

DeJesus, Ed is from United States and they belong to Oracle Magazine and they are from Redwood City, United States got related to this Particular Journal. and DeJesus, Ed deal with the subjects like Databases; Information/Knowledge Management; Software Applications

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