10.1 Sources of errors in quantum systems

Quantum systems face various error sources that can disrupt computations. Decoherence, gate errors, and measurement inaccuracies all contribute to unreliable results. These issues stem from interactions with the environment and imperfections in quantum hardware.

Environmental factors like thermal noise and electromagnetic interference further complicate matters. Quantum noise, arising from the system's inherent nature, sets fundamental limits on accuracy. Understanding these error sources is crucial for developing effective error correction and mitigation strategies in quantum computing.

Sources of Errors in Quantum Systems

Sources of quantum system errors

Top images from around the web for Sources of quantum system errors

• 

  Optimizing Quantum Error Correction Codes with Reinforcement Learning – Quantum View original

  Is this image relevant?

• 

  Always-On Quantum Error Tracking with Continuous Parity Measurements – Quantum View original

  Is this image relevant?

• 

  Optimizing Quantum Error Correction Codes with Reinforcement Learning – Quantum View original

  Is this image relevant?

• 

  Always-On Quantum Error Tracking with Continuous Parity Measurements – Quantum View original

  Is this image relevant?

1 of 2

Top images from around the web for Sources of quantum system errors

• 

  Optimizing Quantum Error Correction Codes with Reinforcement Learning – Quantum View original

  Is this image relevant?

• 

  Always-On Quantum Error Tracking with Continuous Parity Measurements – Quantum View original

  Is this image relevant?

• 

  Optimizing Quantum Error Correction Codes with Reinforcement Learning – Quantum View original

  Is this image relevant?

• 

  Always-On Quantum Error Tracking with Continuous Parity Measurements – Quantum View original

  Is this image relevant?

1 of 2

• Decoherence causes loss of quantum coherence due to interaction with the environment, evolving the quantum state into a classical mixture
  • Amplitude damping leads to loss of energy from the quantum system to the environment (relaxation)
  • Phase damping results in loss of phase information without energy dissipation (dephasing)
  • Depolarization causes uniform loss of coherence in all directions, randomizing the quantum state
• Gate errors arise from imperfections in the implementation of quantum gates, introducing inaccuracies in quantum operations
  • Calibration errors stem from inaccuracies in control parameters such as pulse duration or amplitude, leading to imprecise gate operations
  • Crosstalk involves unintended interactions between qubits during gate operations, causing errors in the targeted qubits
  • Leakage occurs when the quantum system transitions to states outside the computational subspace, affecting the reliability of computations
• Measurement errors result from inaccuracies in the readout of quantum states, affecting the reliability of measurement outcomes
  • Readout noise introduces errors in distinguishing between different measurement outcomes (false positives or negatives)
  • Measurement crosstalk involves the unintended influence of measurements on other qubits, leading to errors in the measured qubits
  • State preparation errors arise from inaccuracies in initializing the desired quantum state, affecting the starting point of computations

Effects on quantum computation reliability

• Decoherence limits the coherence time available for quantum computations, causing the quantum state to deviate from the intended evolution and reducing the fidelity of quantum operations and accuracy of results
  • Shorter coherence times restrict the depth and complexity of quantum circuits that can be reliably executed
  • Decoherence errors accumulate over time, leading to a gradual degradation of the quantum state and computational accuracy
• Gate errors introduce inaccuracies in the implementation of quantum algorithms, accumulating over the course of a computation and leading to erroneous outcomes
  • Imperfect gate operations cause the quantum state to deviate from the intended transformations, affecting the correctness of the computation
  • Error correction techniques, such as quantum error correction codes (surface codes), are required to mitigate the impact of gate errors and maintain computational reliability
• Measurement errors affect the reliability of readout results and can propagate errors to subsequent computations that depend on the measurement outcomes
  • Inaccurate measurements lead to incorrect interpretations of the quantum state, affecting the validity of the computational results
  • Error mitigation strategies, such as repeated measurements or ancilla-assisted readout, are employed to improve the reliability of measurement outcomes

Environmental noise impact

• Thermal noise, caused by the thermal motion of atoms in the environment, induces random fluctuations in the energy levels of qubits, leading to decoherence and gate errors
  • Higher temperatures increase the thermal noise and accelerate the decoherence process, reducing the coherence time of qubits
  • Cryogenic cooling systems (dilution refrigerators) are used to minimize thermal noise by operating quantum systems at extremely low temperatures
• Electromagnetic interference from stray electromagnetic fields can couple to the quantum system, introducing unwanted transitions and phase shifts in the quantum state
  • External electromagnetic sources, such as nearby electronic devices or power lines, can disrupt the precise control and manipulation of qubits
  • Shielding and filtering techniques, such as Faraday cages and low-pass filters, are employed to minimize the impact of electromagnetic interference on quantum systems
• Vibrational noise caused by mechanical vibrations can affect the stability of the quantum hardware, causing fluctuations in the control parameters and introducing gate errors
  • Vibrations from the environment, such as building vibrations or acoustic noise, can disturb the precise alignment and control of quantum devices
  • Isolation and damping mechanisms, such as vibration isolation tables and acoustic enclosures, are used to reduce the influence of vibrational noise on quantum systems

Concept of quantum noise

• Quantum noise represents the fundamental limit arising from the quantum nature of the system and its interaction with the environment
  • Shot noise originates from the discrete nature of quantum measurements, introducing uncertainties in the measurement outcomes
  • Quantum fluctuations arise from the inherent uncertainties in the quantum state due to the Heisenberg uncertainty principle, setting a lower bound on the achievable precision
  • Quantum backaction refers to the disturbance caused by the measurement process itself, influencing the quantum state being measured
• Quantum noise sets a lower bound on the achievable accuracy and fidelity of quantum operations, introducing errors in state preparation, gate operations, and measurements
  • Quantum error correction techniques, such as the use of stabilizer codes (Steane code) or topological codes (surface codes), are employed to detect and correct errors caused by quantum noise
  • Noise-resilient algorithms, such as variational quantum algorithms (VQE) or quantum error mitigation techniques (zero-noise extrapolation), are designed to mitigate the impact of quantum noise on computational accuracy